Ultrasonic long bone imaging is a potentially valuable index of fetal growth. Reported here are fetal limb measurements in normal pregnancies, produced with readily available ultrasound equipment and described using simple statistical techniques. Lengths of femur, humerus, tibia/fibula, and radius/ulna are related to gestational age. Femur and humerus measurements are also related to biparietal diameter. Linear correlation is high and with few exceptions these results confirm those of other investigators. Comparability between these data and previously published work is examined and the utility of these standards of growth discussed. Long bone imaging is confirmed as being reliable, reproducible, and a viable alternative to the measurement of biparietal diameter in the biophysical assessment of fetal development.