A mother's ability to identify consistently what she perceives to be communicatively salient behaviours is considered to be fundamental to the process of responding sensitively to prelinguistic infants. The present study investigated the ability of 35 mothers to identify consistently what they perceived to be communicative acts by infants at three ages (0;6, 0;9, and 1;0). Each mother coded the same videotape of her infant's behaviour on two occasions, three months apart, and observed measures of agreement (consistency) between coded records were obtained. A randomization procedure was used to provide distributions of chance levels of agreement between coded records with which observed measures were compared. Comparisons of the mothers' coded records indicated that they were able to identify infants' communicative acts consistently at each age.