The clinical course of melanoma of the skin diagnosed during pregnancy was compared with a control population of women with melanoma that occurred during the childbearing years, as recorded by the Connecticut Tumor Registry. The survival at three and five years for the 12 patients whose melanoma developed during pregnancy was significantly worse than for 175 nonpregnant controls (five-year survival 55% for pregnant women compared with 83% for nonpregnant women, P less than 0.05). Melanoma during pregnancy tended to occur more often on the trunk, a prognostically poor site, and at more advanced stage of disease than in nonpregnant women. However, when pregnant patients were matched to random, nonpregnant case-controls by age, anatomic site of primary lesion, and stage at diagnosis, three- and five-year survivals were not different. The number of pregnant women observed among this group of women was not substantially higher than expected, when estimated from Connecticut live birth rates: 13.3 pregnancies were expected and 12 pregnant women were actually observed. However, an unknown number of pregnancies end in abortion, making more exact estimates impossible. Melanoma occurring during pregnancy usually carries a poor prognosis, but once the disease is diagnosed, the course is not worse than expected considering stage of disease and primary site.