Objective. To determine the proportion of postpartum women aged 15–49 in Peru who are susceptible to rubella, in order to help address strategies to eliminate rubella and to prevent congenital rubella syndrome (CRS) in the country. Methods. A cross-sectional survey was conducted during March and April 2003 in six main regional hospitals, in the three geographic regions (coast, mountain, and jungle) of Peru. For the postpartum women who provided written informed consent, a questionnaire was administered and a blood specimen was collected. Sera were tested for rubella immunoglobulin G (IgG) antibody, using a commercial enzyme-linked immunosorbent serologic assay (ELISA) kit. Univariate, bivariate, and multivariate analyses were carried out to assess risk factors for susceptibility. Results. In total, 1 236 postpartum women were enrolled. The overall proportion of IgGantibody negative women was 12.8% (95% confidence interval (CI): 10.9%–14.6%). Bivariate analysis found the following variables associated with susceptibility: living in the jungle region (odds ratio (OR) = 1.65; 95% CI: 1.13–2.42); age < 19 years (OR = 2.02; 95% CI: 1.35–3.03); being a housewife (OR = 1.69; 95% CI: 1.12–2.55); and having 11 years of education (OR = 2.12; 95% CI :1.20–3.75). Multivariate analysis found the following variables were associated with susceptibility: living in the jungle region (OR = 1.67; 95% CI: 1.13–2.46); age < 19 years (OR = 1.62; 95% CI: 1.07–2.47); having < 4 children born alive (OR = 1.85; 95% CI: 1.00– 3.40); and having 11 years of education (OR = 2.07; 95% CI: 1.16–3.71). Conclusions. The proportion of postpartum women at the study sites who were found to be susceptible to rubella was 12.8%, placing Peru among the countries facing a moderate level of risk for the occurrence of CRS cases. The findings suggest the need to also provide the rubella vaccine to other population groups, especially women of childbearing age.