Objective: To evaluate differences between adults who participated in a secondary prevention of ischaemic heart disease (IHD) programme and those who did not. Design: Population-based cohort study. Setting: A random selection of 12 Irish general practices. Participants: A total of 493 adults with IHD identified in 2000/2001. Intervention: Medical records search and postal questionnaires in 2000/2001 and 2005/2006. Main outcome measures: Differences in demographic characteristics and indicators of process of care and risk factor management between participants and non-participants. Results: Multiple logistic regression confirmed that female gender was associated with a reduced likelihood of participation in the secondary prevention programme [odds ratio (OR) 0.53 (95% CI: 0.32-0.87)], while an adequately controlled total cholesterol level was associated with an increased likelihood of enrolment [OR 1.82 (95% CI: 1.18-2.80)]. Conclusions: There is limited evidence that biases, which have been shown to affect participation in research, also affect participation in care programmes in everyday practice. A gender bias appears to have affected the enrolment of participants for the secondary preventive programme considered by this study, with enrolment favouring men with well-managed cholesterol. Reimbursement dependent upon patient adherence may incentivise the enrolment of adherent patients, although the influence of patient choice is unclear: the need to maintain records relating to patients who opt out of such interventions is thus highlighted.