 The Engage study is a longitudinal bio-behavioral cohort study of gay, bisexual and other men who have sex with men, GBM, in Toronto, Montreal and Vancouver. In Montreal, the study had the most success due to higher proportions of older participants and lower levels of homophily. Additionally, Montreal had the lowest percentage of participants with an annual income greater than a binisher, 000, suggesting that financial interests were not the primary motivation for participation. This article was authored by Jordan M. Sang, Peter Golemian, Lu Wang and others.