It is difficult to study the contribution of fathers' antisocial behaviour to children's development because fathers with behavioural problems are often absent or reluctant to participate in research. This study examines whether mothers' reports about their children's fathers' antisocial behaviour can be substituted for interviews with fathers. Both members of 67 couples (N = 134) were interviewed separately and independently about the men's lifetime antisocial behaviour. There was strong relative agreement: the women's reports about men's antisocial behaviour and the men's self-reports about the same behaviour were highly correlated. However, there was poor agreement about absolute level: compared to men's self-reports, women reported fewer of the men's antisocial behaviours. Women's reports provide a reliable index of men's relative standing in a distribution and can be used in research about their children's fathers, but should not be used to make diagnostic decisions about men's antisocial disorders.