The aim of this study was to assess sexual activity, condom use and disclosure of HIV infection status among HIV-infected women 3-12 months after delivery and to identify factors associated with unsafe sex. A cross-sectional study was carried out on 480 HIV-positive sexually active new mothers in 48 primary health care clinics in Nkangala District. Post-natal women were recruited by systematic sampling (every consecutive patient over a period of 2 months) and responded to a questionnaire. Overall, 31.9% reported unsafe sex with an HIV-uninfected of unknown-status partner. In multivariate regression analysis, not having disclosed their HIV status, having experienced physical partner violence, lack of male involvement and not having attended a support group were associated with unsafe sex. Several risk factors for unsafe sex post-natally have been identified and can be utilised in post-partum sexual health education programmes.