Found 60% of children 7-12 years old with cystic fibrosis to have a parent-reported behavior problem and 62% met the criteria for a DSM-III diagnosis based on a structured clinical interview with the child. Mixed internal and external behavior problem patterns and diagnoses of anxiety and oppositional disorder were most frequent. Support was provided for the hypothesized psycho-social/mediational roles of child perception of self-worth and maternal anxiety in child adjustment. Together, the variables of the transactional stress and coping model accounted for 39 and 43% of the variance in mother-reported internalizing and externalizing behavior problems and for 68% of the variance in child-reported problems.