Summary A controlled study on crying of fifty individual babies was made in a hospital during April, 1944. Four observers took turns in recording the amount of crying in minutes and the estimated causes of the crying. The amount of crying for the baby with the least crying activity was 386 minutes during eight days, or 48.2 minutes per day. The baby who cried the most totaled 1,947 minutes during eight days, or 243 minutes per day. The average crying per infant amounted to 936 minutes during eight days, or 117 minutes per day. A definite correlation between crying and nursing care was noted: the more care, the less crying. The distribution of the total crying time of the fifty babies was bell-shaped. A graph of the crying of the average baby per day for eight days resulted in a smooth curve, while that of any individual infant climbed and fell in an irregular manner. Three different methods were used to evaluate the relation of crying to weight gain and feeding. The results were vague, except for that of the last method, which showed 17.8 minutes less crying daily in favor of the good feeders. An attempt was made to estimate the causes of crying. Obvious causes, such as hunger, vomiting, soiled and wet diapers, and unknown reasons, were tabulated in minutes and number of spells. The most clear-cut result of our study of the causes of neonatal crying is the demonstration of the importance of unknown reasons. In total minutes of crying this group of reasons closely approaches the amount for hunger and in the number of crying spells it exceeds it.