This study sought: (1) to develop and collect evidence of reliability and validity for self-report instruments to measure cognitions about the experience of having a child with a disability; and (2) to examine the relationship of these cognitions with measures of stress and well-being among parents of children with disabilities. Cognitions included causal attributions, perceptions of mastery/control, social comparisons, and positive contributions. The study surveyed 1270 parents representing 893 families of persons with disabilities. Compared to other research, results indicated weaker relationships between characteristics of the child and parent and measures of stress. Results suggest that the way that parents think about having and raising a child with a disability is as good a predictor of how much stress they experience as more objective aspects of their situation such as child's age or family income. The study provided moderate support for S. E. Taylor's theory of cognitive adaptation, especially in regard to the role of making social comparisons and construing positive benefits with adjustment. However, little evidence was found to show that causal attributions and perceptions of control serve to reduce stress or bolster well-being. A description of the Family Perceptions Research Project which undertook the study is appended. (29 references.) (JDD)