Couples reported their condom use at each monthly visit. Condom use was summarized for the duration of the study as never, sometimes (1 to 90 percent of sexual contacts), nearly always (>90 percent of sexual contacts), or always. Panel A shows the frequency of symptomatic HSV-2 infection in the susceptible partner at each level of condom use. Panel B shows the frequency of acquisition of HSV-2 infection in the susceptible partner at each level of condom use. In each panel, the T bars depict the upper end of the 95 percent confidence interval.