This investigation evaluated the utility of a new assessment tool based on a competency/coping skills model in predicting medical compliance of adolescents with cystic fibrosis. The Medical Compliance Incomplete Stories Test (M-CIST) and an assessment of several coping behaviors identified as assisting chronically ill children in their adaptation were used with 40 adolescent inpatients aged 13-23. These data were compared to objective measures of the patient's medical compliance. The total M-CIST score was shown to be positively correlated with compliance and to significantly discriminate between compliant and non-compliant groups. Although the assessment of coping behaviors also discriminates significantly between the two groups, it provided no additional power when used in common with the M-CIST. The data identified differences in coping behaviors between compliant and non-compliant patients which may prove useful to clinicians treating adolescents with cystic fibrosis.