Parents are now primarily responsible for the at home assessment and treatment of their children's pain following minor surgery. Although some research has suggested that parents underestimate their children's pain following surgery, no behavioral measure exists to assist parents in pain assessment. The Postoperative Pain Measure for Parents was developed based on cues parents reported using to assess their children's pain (e.g. changes in appetite, activity level). The purpose of the present study was to develop and validate this measure by examining the relation between parent-report of child behaviors and child-rated pain. Subjects were 110 children (56.4% male) aged 7-12 years undergoing day surgery at a tertiary-care children's hospital and their parents. Parents and children completed a pain diary for the 2 days following surgery. Children rated their pain and emotional distress and parents rated the presence or absence of specific behaviors from a checklist. Correlations were conducted between each of the 29 behavioral items and child-rated pain on Day 1; 14 items with correlations less than 0.30 were dropped. The remaining 15 items were subjected to a principal axis factor analysis. A one-factor solution was the best fit for the data. The items were then summed to yield a total score out of 15. Internal consistency reliabilities for the measure and correlations with child-rated pain were high on both days following surgery. Child-rated pain and emotional distress were moderately correlated. The Postoperative Pain Measure for Parents was also positively correlated with child-rated emotional distress on both days following surgery. As child-rated pain decreased from Day 1 to Day 2, so did scores on the behavioral measure. The Postoperative Pain Measure for Parents was successful in discriminating between children who had undergone no/low pain surgeries and children who had undergone moderate to high pain surgeries. There were no significant differences in scores on the behavioral measure for child age or sex. Using a cut-off score of six out of 15, the measure showed excellent sensitivity (> 80%) and specificity (> 80%) in selecting children who reported clinically significant levels of pain. This study provides preliminary evidence for the use of the Postoperative Pain Measure for Parents as a valid assessment tool with children between the ages of 7-12 years following day surgery. It is internally consistent and strongly related to child-rated pain. Future research should explore the use of this measure with a younger sample and children with developmental delays.