Describes the development of a laboratory method of assessing coercive discipline (CD) for young children. A videotape with 14 clips of children engaged in varying degrees of risky behaviors and misbehaviors was produced, and 120 parents of 1-3 yr olds recorded on a computer when and how they would intervene. A CD scale was developed from the parental responses. This scale was then compared with other measures of coercive parent discipline with 100 mothers of 18-mo-olds. A CD construct, which included the lab task, was developed with good internal agreement. In a 2nd study, with 80 toddlers observed in playgroups from 18-30 mo of age, the video-based assessment correctly classified 95% of the families observed to be coercive with their children, a 77% relative improvement over chance. The CD scale from the lab task was significantly related to both the mothers’ ratings of aggression and to observed aggression in the playgroups.