The aim of the study is to identify factors influencing infants' crying behaviour (total crying duration, length of crying bouts, and frequency of crying). The searching for variables explaining inter-individual differences requires a sufficient stability of the cry parameters at least over short time intervals. Thus, a second aim is to assess the intra-individual stability of the crying behaviour in an age range from 3 to 12 months. Sixty-two mother-child dyads participated in the study. The results show substantial stabilities of the crying behaviour of infants between 3 and 12 months of age. This is related to the amount of crying as well as to the pattern of crying shown by the children over a 24 h interval. The typical cry pattern is characterized by peaks at 12.00 h and early in the evening, although there are large individual differences between the children with regard to cry durations at each hour of the day. Regarding the cry durations at 3 months of age, birth complications and the perceived emotional atmosphere in the mothers' family of origin are the major contributing factors.