The incidence of gestational diabetes mellitus (GDM) is increasing in the United States. Universal GDM screening is recommended, although evidence of benefit is lacking. Treatment of GDM reduces the risk of shoulder dystocia, preeclampsia, and macrosomia. Intensive treatment is more effective than less-intensive treatment. Traditional management includes diet, exercise, and short- and intermediate-acting insulin regimens. Use of metformin and glyburide is controversial, but evidence supporting safety and efficacy is accumulating. Postpartum screening with a glucose tolerance test rather than a fasting blood glucose level should be performed 6 weeks after delivery.