While at the University of Ibadan he was Visiting Lecturer at University College, London; Visiting Professor at Iowa State University, Ames, Iowa, USA; Johns Hopkins University, Baltimore, MD, USA, and University of Ife now (now OAU) at Ile-Ife. With an urge for greater challenges, Prof. Adeniyi voluntarily retired from the public sector in 1990 and set up a private consultancy firm and he was President of Development Research Bureau (DRB), a firm of Consultants based in Bodija, Ibadan. He was Chairman of ADABOL Investments Ltd. and ADABOL Petroleum Company as well as Vice-Chairman of Western Zone of Independent Petroleum Marketers' Association of Nigeria (IPMAN). He was a regular Consultant to the United Nations Development Programme (UNDP) and was formerly Coordinator for Nigeria's UNDP Fourth Country Programme which identified the Planning and Development Needs on which the UNDP Programmes/Projects in Nigeria are based. Prof. Adeniyi had considerable experience in Development Planning and had been connected with Development Planning exercises in this country for nearly three decades. For nearly twenty years, he was a member of the Joint Planning Board responsible for planning and review of Development Plans at the national level. He was a member of the Western State Economic Advisory Council up to the creation of new States in 1976. Earlier on, he was a member of the Western State Health Council and Chairman Ondo Zonal Health Board 1975-1976 and also a member, Panel of Experts on the Development of Urban Centres and Regional Planning of Ondo State 1976-1977. He was a pioneer Member of the Board of Directors, Ondo State Water Corporation 1976-1978; member Planning Committee of Ondo State University 1980-1981; Chairman, Board of Directors, Nigerian-Romanian Wood Industries (NIROWI) Ondo 1980-1981. As a Director of the Nigerian Institute of Social and Economic Research (NISER), Ibadan he coordinated the Survey of Resources for the former 19 states of Nigeria, 1978-1982. Prof Adeniyi also served in other States as Consultant/Planner to Metropolitan Kano Planning Development Board and as Consultant/Adviser to the defunct North-Western State, Niger State and Kwara State on the preparation of their Development Plans. At the Local level, Prof Adeniyi was Patron to many Social and Cultural Organisations and formerly Secretary-General of Idanre Students' Union, and the Secretary of Bodija Estate Houseowners/Residents Association. He was also a nominated councillor of Local Government, Ondo State 1975-76. He served in varied roles in Idanre Rocks Club including as President. He also was the President of Rotary Club of Bodija, Ibadan, 1996-97 and was Director, International Services, Rotary District 9130. At the National level, Prof. Adeniyi has served among other bodies, as member, National Council on Statistics 1972-1974; Member, National Census Board 1972-75; Member, Panel of Experts on Validation of the 1973 Population Census 1975-76; Member, Nigerian National Coordinating Committee on the Human Environment 1974-79; Consultant to the Federal Government on High Level Manpower Development 1974-79; Member, National Policy Development Centre (Think-Tank Board) 1976-79; Consultant, Federal Capital Development Authority 1977-80; Pioneer Secretary-General, Social Science Council of Nigeria 1982-85; President, Nigerian Society for Environmental Management and planning (SEMP) 1993ff; Member, Governing Council, Industrial Training Fund 1984-86; Chairman, and Professional Committee of the Administrative Staff College of Nigeria (ASCON) 1987-88; Chairman, Medium Term Plan for Nigeria's National AIDS Control Programme 1992-93; Chairman, Governing Council, Nigerian Institute of Transport Technology (NITT), Zaria, 1987-94. At the International level, Prof. Adeniyi has worked as Consultant and Resource Person to the United Nations and its specialised agencies such as UNESCO, UNICEF,UNFPA, UNDP, IDEP, UNCHP, FAO, UNEP, UNECA, ILO, UNAIDS, United Nations University; WHO, Ford Foundation, Family Health International, USAID; etc. as well as the World Bank. He has also worked actively with international Non-governmental Organizations (NGOs) such as Society for International Development (SID) (was a member of its Governing Council 1982-85); North-South Round Table; Council for the Development of Economic and Social Research in Africa (CODESRIA); International Federation for Housing and Planning (IFHP); World Social Prospects (AMPS); African NGOs Environment Network (ANEN); Confederation of African Medical Association and Societies (CAMAS), etc. He worked as a member of the Preparatory Group of the Federal Government of Nigeria for the Founding of the Economic Community of West African States (ECOWAS). He served as a Consultant to UNAIDS (October/November 1999) for the preparation of the National Strategic framework for HIV/AIDS Activities in Uganda 2000/1 - 2005/6. He is a also a Review Consultant to the Democracy and Governance (D&G) Project of CEDPA (USAID). In recognition of his contributions to international development, he was appointed one of the twenty eminent scientists with wide experience to serve as members of the Scientific Council of Pan-African Social Prospects Centre (CPPS). He has also been listed in many ‘WHO is Who’ at both national and international level. Prof. Adeniyi combines very rich experience in research, consultancy, management and policy issues and has been exposed to several challenges in the application of his expertise on development issues both at Community, State Federal and International levels. Earlier on, he was between 1976 ad 1979 the Project Director of the Development of Priority Ratings Study for the National Board for Technical Education (NBTE) Kaduna, designed to determine the priority of courses to be offered in Nigerian Polytechnics. He was also the Project Director of the Lagos State Audit of Local Governments in Lagos State 1978-88. In addition, he coordinated the 1994 National Orientation Workshop for Chairmen and Members of Local Government Caretaker Committees for States in the Western Zone. He also coordinated the study and preparation on behalf of the Federal Ministry of Trade and Tourism the Nigerian Trade Review Mechanism for GATT (Now WTO) 1990-91. Prof. Adeniyi was actively connected with planning/development issues and he coordinated the UNDP study on Poverty Alleviation in the South-Western (Geo-Political Zone) States of the Country as well as the UNICEF Study on Compact 20/20 Initiative designed to restructure government expenditure in favour of social services of education, health water etc, - as a means of poverty alleviation in the country. He also coordinated for the National Planning Commission the South Investment Trade and Technology Data Exchange Centre (SITTDEC) Project for the set up of Nigeria's National Focal Point.