The heated debate over the limited impact of integrated pest management (IPM) in Central American agriculture suggests that we need to investigate the mechanisms of IPM technology generation. CATIE/MAG-IPM Nicaragua initiated a comparative study of two prototypic models with tomato farmers in the Sébaco Valley, in 1990-91. I created two ideal types from the literature: the scientist-led and farmer-led models. Each model was represented by three different communities. The study focused on the: 1) technology generation process, 2) IPM technologies and farmer opinion of IPM, 3) forms of participation and empowerment by farmers and scientists, and 4) institutionalization of the two models. The investigation methodology consisted of intensive pre- and post-program interviews, participant observation, and statistical analysis of experimental insect and production variables. This paper focuses on farmer participation, empowerment, and evaluation of the two models. In the farmer-led model, farmer participation was greater than in the scientist-led model in number of farmers and farm units involved. They achieved five forms of influence, and six out of eight levels of empowerment in the farmer-led model. In the scientistled model, farmers achieved two forms of influence and two out of eight levels of empowerment. Farmer evaluations were varied and complex. In general, farmers in the scientist-led model encouraged CATIE/MAG-IPM to host more meetings and expand farmer involvement. In the farmer-led model the farmers enjoyed the biological information, new technologies, and discussion. They suggested changes for future meetings.