Despite the urgency of improving an understanding of sexual cultures in the face of a globally devastating HIV epidemic, methodological reflection and innovation has been conspicuously absent from qualitative research in recent years. Findings from fieldwork on condom use among young people in Mozambique confirm the need to remain alert to the ideological and linguistic bias of applied methods. Interviewing young people about their sexuality using a conventional health discourse resulted in incorrect or socially acceptable answers rather than accurate information about their sexual behaviour. Young people's resistance to enquiry, the paper argues, is due to ideological contradictions between their sexual culture and slang, on the one hand, and Western health discourses associated with colonial and post-colonial opposition to traditional culture and languages, on the other. Mixing colloquial Portuguese and changana sexual slang is constructed around ideas of safedeza and pleasure, while dominant health discourses address sexuality as both ‘risky’ and ‘dangerous’. In order to gain a deeper understanding of sexual cultures and to make HIV prevention efforts relevant to young people, it is suggested that researchers and policy makers approach respondents with a language that is sensitive to the local ideological and linguistic context.