Screening for gestational diabetes mellitus by a 1-hour glucose challenge test is recommended for all pregnant women between 24 and 28 weeks of pregnancy. Measurement of capillary blood glucose with a reflectance meter is well known and considered to be accurate, reliable, less costly, and more convenient than the laboratory test of plasma glucose. One hundred eighty-one pregnant women were tested with both a 1-hour glucose challenge test by capillary blood glucose and a 3-hour glucose tolerance test by venous plasma glucose. The diagnosis of gestational diabetes mellitus was made by the standard criteria on the 3-hour glucose tolerance test. The receiver operating characteristic curve was used to determine the optimum threshold value. There were seven cases of gestational diabetes mellitus detected during this study period, producing an incidence of 3.9%. The threshold value for the 1-hour glucose challenge test by capillary blood glucose was 9.0 mmol/L (163 mg/dL); the test has a sensitivity, specificity, predictive value, and likelihood ratio of 0.857, 0.868, 0.207, and 6.48, respectively. This test was at least as accurate as a 1-hour glucose challenge test by venous plasma glucose. Given its advantages, such as lower cost, simplicity, better patient acceptance, and immediate availability of the result, capillary blood glucose testing should be considered for screening of gestational diabetes mellitus in the office setting.