Gestational diabetes occurs in 5 to 9 percent of pregnancies in the United States and is growing in prevalence. It is a controversial entity, with conflicting guidelines and treatment protocols. Recent studies show that diagnosis and management of this disorder have beneficial effects on maternal and neonatal outcomes, including reduced rates of shoulder dystocia, fractures, nerve palsies, and neonatal hypoglycemia. Diagnosis is made using a sequential model of universal screening with a 50-g one-hour glucose challenge test, followed by a diagnostic 100-g three-hour oral glucose tolerance test for women with a positive screening test. Treatment consists of glucose monitoring, dietary modification, exercise, and, when necessary, pharmacotherapy to maintain euglycemia. Insulin therapy is the mainstay of treatment, although glyburide and metformin may become more widely used. In women receiving pharmacotherapy, antenatal testing with nonstress tests and amniotic fluid indices beginning in the third trimester is generally used to monitor fetal well-being. The method and timing of delivery are controversial. Women with gestational diabetes are at high risk of subsequent development of type 2 diabetes. Lifestyle modification should therefore be encouraged, along with regular screening for diabetes.