In an effort to assess the efficacy of the oral glucose tolerance test to detect patients with gestational diabetes mellitus who require therapeutic measures to maintain normoglycemia, we compared the results of an oral glucose tolerance test with those of a home glucose profile consisting of three postprandial glucose values in 250 pregnant women. The OGTT overestimated the occurrence of hyperglycemia by 28%, while the home glucose profile underestimated the occurrence of hyperglycemia by 5%. Pregnancy outcome was not significantly different between spontaneously normoglycemic women and those who required therapy. One cannot effectively identify the ten percent largest infants in the population by screening for gestational diabetes.