The ways in which couples communicate about microbicides is likely to influence microbicide uptake and usage. We collected quantitative data about whether women in a microbicide trial discussed microbicides with their partners and explored communication about microbicides during 79 in-depth-interviews with women enrolled in the trial and 17 focus-group discussions with community members. After 4 weeks in the trial, 60 % of 1092 women had discussed microbicides with their partners; in multivariate analysis, this was associated with younger age, clinic of enrolment and not living in households that owned cattle. After 52 weeks, 84 % of women had discussed microbicides; in multivariate analysis, this was associated with not living in households that owned cattle, not living in a household that relied on the cheapest water source, allocation to 0.5 % PRO2000 gel and consistent gel adherence. Qualitative findings highlighted that women in committed relationships were expected to discuss microbicides with their partners and preferred to use microbicides with their partner's knowledge. Women had different reasons for, and ways of, discussing microbicides and these were influenced by the couple's decision-making roles. Although there was tolerance for the use of microbicides without a partner's knowledge, the women who used microbicides secretly appeared to be women who were least able to discuss microbicides. In KwaZulu-Natal, socio-cultural norms informing sexual communication are amenable to microbicide introduction.