This study assesses the frequency of gestational diabetes in a multiethnic teenage pregnancy clinic. One hundred thirty-seven women age 12-18 years were screened with a 1-hour 50-gm glucola test at 24-34 weeks gestation. Screening tests were positive in 5.8% of these teenagers, of whom half were obese. Gestational diabetes was documented in two primiparas (1.4%). Maternal weight gain was excessive in 54%, and 8.7% of the total group had macrosomic infants. We conclude that gestational diabetes should be screened for in all young pregnant women with the screening test recommended by the Second International Workshop-Conference on Gestational Diabetes.