Assessment of quality of life (QOL) in young adults has become an increasingly important field of research as information on the QOL of children and adults accumulates. The purpose of this study is to report on the development of the Young Adult Quality Of Life (YAQOL) instrument, a measure of QOL for young adults aged 18-25. The YAQOL, which is comprised of 14 multi-item scales that assess physical health and aspects of psychological well-being, social relationships, role function, and environmental context, was administered to a general population sample of 751 young adults. Scale structure was confirmed by item-internal consistency, item discriminant validity, and inter-scale correlations. Reliability coefficients ranged from 0.88 to 0.63 across scales (mean = 0.73). Eight YAQOL scales discriminated clearly between young adults with and without chronic physical conditions, 12 scales discriminated between young adults with and without personality disorder, and negative associations were demonstrated between YAQOL scale scores and psychiatric disorder symptoms. Demographic differences in the YAQOL scales were consistent with theoretical expectations and previous empirical work. Overall, findings support the reliability and utility of the YAQOL as a measure of QOL in young adults in the general population. Additional psychometric properties will continue to be evaluated as more data become available.