Predictors of change in the number of sexual topics parents discussed and responsiveness during sex communication with their preadolescent after participating in a five-session sexual risk reduction intervention for parents were examined. Data were from 339 African American parents of preadolescents enrolled in the intervention arm of a randomized-controlled trial of the Parents' Matter! Program (PMP). Four categories of predictors of success were examined: time and resource constraints, personal characteristics, the parent-child relationship, and parent perceptions of child readiness for sex communication. There were only sporadic associations between success and time and resource constraints for either outcome. Parent perception of child readiness for sex communication was positively associated with discussions of sex topics (b = 1.11, confidence interval [CI]: 0.24-1.97) and parental responsiveness (b = 0.68, CI:0.22-1.15). Although parents face time and resource constraints, most attended at least four sessions, and demographics such as income had limited effects on program success.