We evaluated whether use of a short- or longer-term recall period for condom use was superior for assessing risk of acquisition of incident sexually transmitted infection (STI). Female sex workers (n = 1000) in Madagascar took part in a randomized trial comparing counselling strategies for male and female condom promotion. We explored associations between women's self-reported condom use with clients and non-paying partners and incident STI, examining both short-term recall (last sex act) and longer-term recall (over the past month and year). Self-reported condom use was generally not associated with reduced STI risk, whether measured at the last act or over longer time periods; with clients or non-paying partners; and through unadjusted and adjusted modelling. No condom use measure (short versus longer time periods, with one or both partner types) was strongly predictive of STI, suggesting poor validity.