This study investigates the validity of the Parent Instruction-Giving Game with Youngsters (PIGGY), a newly developed direct-observation system. The PIGGY is a derivative of the Dyadic Parent-Child Interaction Coding System II [DPICS-II; Eyberg, S. M., Bessmer, J., Newcomb, K., Edwards, D., Robinson, E. (1994). Manual for the Dyadic Parent-Child Interaction Coding System-II. "Social and Behavioral Sciences Documents" (Ms. No. 2897)] and the Behavior Coding System [BCS; Forehand, R. L., McMahon, R. J. (1981). "Helping the noncompliant child." New York: Guilford Press] and utilizes a format similar to the more structured Compliance Test [Roberts, M. W., Powers, S. W. (1988). The Compliance Test. "Behavioral Assessment," 10, 375-398]. Using the PIGGY, parents provide standardized commands to their child (e.g., "Put the book on the table"). The parenting skills used to gain compliance (e.g., instruction giving, praise, discipline techniques) as well as child behavior (e.g., noncompliance) are coded on an observation form. In Study 1, 14 "noncompliant" and 14 "compliant" children and their mothers were selected based on parent report of child behavior. The PIGGY differentiated between the two groups on repeat commands, defiant child behavior, and overreactive parenting. Other forms of validity are also reported. In Study 2, the PIGGY was used to monitor the effectiveness of behavioral parent training with a mother and her 3-year-old daughter with oppositional-defiant disorder. Changes in both child and parent behavior were reflected in PIGGY scores. Overall, these studies suggest that the PIGGY may be valuable as both a screening tool and a measure of response to treatment.