Nursing by two mother-infant pairs in a caged colony of Macaca fascicularis was monitored at 1-min intervals for 8 h beginning 8:30 a. m. BST, once a week for 3 months in the summer of 1973. Nursing occupied about 210 min in 8 daylight hours for the infants at 10 weeks of age, and the time spent nursing decreased at the average rate of 9.4 min per week until the infants were about 6 months old. The time spent nursing by the infants studied here resembles closely the times spent nursing by some other macaques and by baboons. In the course of a day the amount of time spent nursing varies significantly with a diurnal peak. If nursing by one mother-infant pair is independent of nursing by the other pair, then the time the two pairs spend nursing together would be a function of the product of the frequencies of nursing by each pair. The expected times for the pairs nursing together based on the hypothesis of independent events were significantly less than the observed times the pairs nursed together. Nursing, therefore, involves a positive influence or imitation of one nursing pair by the other. Nursing sessions involving both mother-infant pairs were longer on the average than sessions involving only one pair.