Parental verbal behavior is often cited as a major precipitating and maintaining factor in the onset and development of stuttering. Parents are frequently counseled to avoid interrupting their stuttering child. The purpose of the present study was to determine (a) whether mothers of preschool stutterers interrupt children's speech more frequently than mothers of nonstutterers, (b) whether stutterers interrupt the speech of mothers more frequently than nonstutterers, and (c) whether there is relationship between interruptive behavior and the occurrence of children's disfluencies. Twenty-four preschool boys (12 stutterers and 12 nonstutterers) and their mothers participated in the study. Ten-min, conversational speech samples of mothers interacting with their own children, unfamiliar stutterers, and unfamiliar nonstutterers were analyzed. Results indicated that mothers of nonstutterers interrupted the disfluent speech of stutterers significantly more often than did mothers of stutterers. Most importantly, all mothers interrupted children's disfluent speech significantly more than they interrupted children's fluent speech. Further, all children demonstrated a tendency to be disfluent when they interrupted a mother.