The data previously reported for serum amylase activity in the blood of pregnant women are conflicting with respect to normal values and the relationship of activity to duration of pregnancy. By use of a DuPont Automatic Clinical Analyzer, amylase activity in serum from the blood of 413 asymptomatic healthy women who were six to 40 weeks pregnant was determined. Samples with amylase activity greater than 100 IU/L were tested for pancreatic and salivary isoenzymes. In every case except one, the isoenzyme levels were normal. In the blood of all women, except this one, the serum amylase activity was less than 150 IU/L and mean serum amylase activity did not correlate with gestational duration. Amylase activities at all gestational ages did not differ from the activity in serum obtained from the blood of women six weeks post partum. The authors conclude that 1) serum amylase levels may be as high as 150 IU/L in the blood of normal pregnant women; 2) serum amylase activities vary widely among pregnant women, but not in a manner related to the stage of gestation; and 3) pregnancy does not cause elevation of serum amylase isoenzyme activity. © 1984 by The American College of Obstetricians and Gynecologists.