The Stockholm-Gotland Cancer Register was used to study the risk of developing second primary malignancies (SPM) in women diagnosed with cancer of the uterine cervix, uterine corpus and ovaries during the period 1958-1992. Among 5,325 patients with uterine cervix cancer, 619 developed SPM. Standardized incidence ratio (SIR) was 1.29 (95% confidence interval (CI) 1.19-1.39). Significantly increased risks were observed for cancer of the colon, rectum, lung, vulva, kidney and bladder. A total of 4,815 women with uterine corpus cancer were followed and 660 SPM were found. The overall SIR was 1.21 (95% CI 1.12-1.30) with significantly increased risk for cancer of the colon, ovary, vulva and bladder. The incidence of leukemia was also significantly elevated (SIR = 3.03; 95% CI 1.70-5.00). Among 5,060 patients with ovarian cancer, 379 SPM were found (SIR 1.49; 95% CI 1.34-1.64). Increased risks of cancer of the colon, rectum, breast, uterine corpus, bladder and leukemia were observed. All three primary sites showed elevated risks of cancer of the colon and bladder. For patients with a primary cancer of the corpus and ovary an elevated risk of leukemia was also noted. The conclusion from these findings is that SPM to some extent can be explained by previously known factors, i.e. treatment and common risk factors. However, further studies concerning the role of common etiology, for instance hereditary and hormonal factors, are needed to increase the knowledge on the etiology of second primary malignancies.