The present study was designed to investigate variables associated with mother-child interaction patterns of Attention Deficit Hyperactivity Disorder(ADHD), and also to evaluate short-term effects of stimulant medication on the behaviors of ADHD children and their mothers during interaction. 15 ADHD boys(ages 5${sim}$10 years) were treated with metylphenidate(0.5mg/kg per day) for 1 month, and their behaviors as well as their mothers for the 10 minute free play and 20 minute task performance period were videotaped through one-way mirror. The childrens attention was also evaluated using the Continuous Performance Task(CPT) and ratings of their hyperactive behaviors were obtained from their mother prior to the treatment. The videotaped interaction were rated according to the Response Class Matrix developed by Mash, Terdal & Anderson(1973). Results indicated that percentage of behavior of the mother and child during interaction was highly correlated with each other, which, in turn, was highly correlated with the symptom severity of the ADHD child. That is the more severe the cognitive and behavioral symptoms of ADHD, the more negative the interaction behavior pattern was. After 4 weeks of stimulant medication the mothers as well as the ADHD children showed a significant decrease in the percentage of negative-aggressive behavior during the task performance period. The results indicated that negative interaction behavior of the mothers was in large part a response to the negative behavior of their ADHD children.