Five hundred ninety-three nonstress tests were performed on 41 obstetric patients, at gestational ages ranging from 20 to 40 weeks. Diagnoses included 10 cases of prematurity, six cases of diabetes mellitus, five cases of collagen-vascular disease, five cases of poor obstetric history, three cases of cardiac arrhythmia, and one case each of asthma, polyhydramnios, leukemia, nonimmune fetal hydrops; and eight volunteers were without high-risk factors. All neonates had a 5-minute Apgar score greater than 8; 29 neonates weighed greater than or equal to 2500 gm, 12 weighed less than 2500 gm, and four weighed less than 1500 gm. One neonate died of prematurity, and one was small for gestational age. There were no congenital anomalies. There was a significant difference in the number of reactive nonstress tests and nonreactive nonstress tests between the 20- to 24-week, 24- to 28-week, 28- to 32-week, and 32- to 36-week gestational age groups. The increased incidence of nonreactive nonstress tests at earlier gestational ages may have clinical implications.