In a cohort of 1200 individuals experiencing an index infection of gonorrhoea or chlamydia in a rural North Carolina county, we studied the risk factors for re-infection within 16 months. The occurrence of asymptomatic re-infection was estimated from a sample of controls. Re-infection with either of the two STDs occurred in one-quarter (24%) of the study participants and 22% of the controls. The factors associated with re-infection were age less than 25 years, African-American race, male sex, and infection prior to the index infection. The behavioural and attitudinal variables tested were not associated with re-infection. The patterns of re-infection in this study do not provide guidance for targeting resources toward a subgroup of the clinic population. Structuring clinical services to make them more available and acceptable to all potential clinic clients can contribute to decreasing the duration of infections. Lowering the community prevalence in this way will then decrease the likelihood of re-infection rates.