The aim of this study was to identify the determinants and patterns of farmers' participation in rnFarmer Research Groups in Adama Woreda. Statistically significant association between rnsocio-economic characteristics and farnlers' participation in Farlner Research Groups rnwere tested. rnThe specific objectives were to: (1) determine the relationship of the socio-demographic and rneconomic factors with farmers' participation; (2) describe the patterns of participation in rnFarmer Research Groups by farmers and researchers and (3) identify constraints to rnfarmers' participation in Fam1er Research Groups. rnThe respondents were selected through a combination of probability proportionate to size rnand systematic sampling, and 120 farmers (60 participants and 60 non-participants in rnFarmer Research Groups) and 20 researchers were included. The respondents were rnselected from 'Awash', 'Batu Degago', 'Ulaga Melka Oba' and 'Wake Miya' peasant rnadministration. rnFocus group discussions, in-depth interviews with key informants, and case studies were rnalso employed to collect qualitative primary data. Quantitative primary data, on the other rnhand, were collected through questionnaire administered by enumerators. Secondary rnsources were also adequately referred from recorded archives to support primary data. rnThe data were analyzed by using both descriptive and inferential statistics like mean, rnfrequency, percentage, chi-square, phi-coefficient and point-biserial correlation. rnThe findings of this study showed that socio-economic and cultural factors such as age, rnhousehold size, educational attainment, size of farm land, and gender are significantly rnrelated to farmers' participation in Farmer Research Groups in Adama Woreda. Based on rnthis finding, it can be concluded that younger farmers relatively participated more in rnFarmer Research Groups. Besides, those farmers who had larger households, large size of rnfarm land and exposition to formal education tend to be more involved in the Farmer rnResearch Groups. rnIn addition, the study indicated that the majority of Farmer Research Group members in rnAdama Woreda have been involved in consultative and collaborative type of rnparticipation. rnThere are constraints to farmers and researchers in participation in the Farmer Research rnGroups in Adama woreda. Expectations for subsidized inputs, farmers' reluctance to rnwork with researchers on the site due to the underestimation of their indigenous rnknowledge in the research process and inadequate motivation of researchers to use rnparticipatory approach have been the most commonly manifested problems among the rnparticipants in Farmer Research Groups.