The Ontario Environmental Farm Plan (EFP) program is a recent sustainable agriculture initiative in the province of Ontario, which is representative of self-initiated participatory forms of research and extension. This thesis sought to identify factors associated with participation within the EFP program, and also to contribute to an understanding of related "sustained" behaviour change. Research involving statistical analysis of mail-back questionnaires from EFP participants revealed that, although most respondents had assessed their operation and implemented sustainable actions, 30% did not take actions. Associated with sustained participation in the program were communication-related characteristics of the farmer, factors associated with perceptions of risk in technical advice and confidentiality, factors characterizing internal motivations, and site-specific factors. Results from personal interviews revealed that the majority of those interviewed exhibited some form of enduring behaviour change after completing the formal stages of the EFP program. These farmers were characterized by internal motivations and implemented changes that were complex or involved adaptations.