A large and increasing proportion of HIV transmissions in sub-Saharan Africa occur within marriage. Condom use within marriage could, therefore, be an important prevention strategy, but there is considerable debate about whether married couples would be willing to use condoms. This paper contributes to this debate by identifying key factors that affect the acceptability of condom use within marriage and actual condom use among men and women in rural Malawi, using three waves of longitudinal data from 2004, 2006 and 2008. Specifically, we focused on the effect of (1) entry into first marriage, (2) respondent's HIV status, HIV perceptions, and risk behaviors, and (3) spouse's HIV characteristics on condom use acceptability within marriage and actual condom use with a spouse or steady partner. Using fixed-effects regression, we found that getting married coincides with a pronounced attitudinal shift regarding the acceptability of condom use within marriage that cannot be explained by differences in fertility status or selection into marriage. In addition, we found that, for women, perceived HIV status of the respondent and spouse generally had greater influence than actual HIV status on the acceptability of condom use within marriage and actual condom use with a spouse or steady partner, even after HIV status is known; while actual HIV status and HIV risk behaviors are generally more important among men. Although condom use within marriage remained low, these findings suggest that attitudes about and use of condoms are susceptible to change and that both marital status and perceptions of risk are important influences on condom use.