Greater use of condoms within marriage would help limit the spread of HIV in sub-Saharan Africa. Using data from the Malawi Diffusion and Ideational Change Project (MDICP), the authors examined the influence that the fidelity norm and the traditional association between marriage and reproduction have on condom use with a spouse. The sample included 749 married couples. The authors used latent class analysis to estimate a "true," or latent measure of condom use by couples based on the individual reports of husbands and wives and to explore the reasons why individuals tend to misreport their use of condoms. They found that married couples with more children were more likely to use condoms and that having been informed by experts about AIDS prevention at home induced men and women to overreport condom use within marriage in a survey but may not necessarily increase the extent to which condoms are used.