The purpose of this paper was to describe the process of developing an instrument for measuring the compliance of adolescents with a chronic disease. The aim was to develop an instrument that could be used in a clinical setting to evaluate the compliance of young people with a chronic disease and to test a theoretical model of compliance, which had been developed along with the instrument. The instrument was originally developed to measure the compliance of adolescents with diabetes and later adjusted to measure the compliance of adolescents with asthma, rheumatoid arthritis and epilepsy. To test and develop the instrument, face and criterion validity, factor analyses, linear structural relations (LISREL) analyses, correlation coefficients and Cronbach's alpha were used. The instrument has 13 background questions and 41 items to measure compliance and factors connected to it.