This article explores the creation of ‘MSM’ as global health category over the course of the HIV and AIDS epidemic, and across country contexts from India to southern and eastern Africa. We conceive of ‘MSM’ as a mode of ‘doing’ and ‘becoming’: ‘MSM-ing’, so to speak. Actor-network perspectives and ethnographic reflections are engaged to elucidate ‘MSM’ as a term that both enables and inhibits communications about sexualities and risks. We consider the term as a plural form of evidencing that offers wider perspectives on flows and boundaries in global health–knowledge making and HIV prevention.