Despite increasing recognition of the importance of measuring the quality of life (QOL) of people with severe mental illness, such assessments are seldom carried out because of the lack of an efficient, easy-to-use, and valid measurement instrument. To facilitate the gathering of QOL information from clients in evaluation, program improvement, or other efforts, the authors present a new short (24-item) self-administered questionnaire called the Quality of Life Questionnaire (QLQ). The questionnaire assesses subjective QOL in seven areas. Evidence for the reliability and validity of the QLQ is based on data gathered from 971 clients with serious mental illness who were receiving publicly funded mental health services at the time of the study. The results of a confirmatory factor analysis using a random split-half procedure indicated that a seven-factor solution fit the data well. Scores on the QLQ also correlated significantly with the client's functioning and satisfaction with services, providing support for the validity of the QLQ. The advantages of the QLQ over existing measures include low-cost administration and some superior psychometric properties.