Health care quality issues for people with developmental disabilities under managed care were explored. Health-related quality was defined in terms of four domains: structure, process, outcome, and satisfaction. Three general problems in the assessment of health care quality were identified: lack of quality measures, patient response problems, and lack of system elements. Selected current measurement systems were described in relation to their use for people with developmental disabilities. An approach to developing quality measures was outlined using Healthy People 2000, Health Plan Employer Data Information Set, and clinical practice issues. The movement toward quality improvement was examined and recommendations presented for steps in developing and measuring health care quality.