n BACKGROUND This paper reports on the validation of the Consumer/Client Primary Care Assessment Tool Adult Edition (PCAT-AE) by assessing the congruence between the theoretically derived measures and the empiric results in terms of the underlying structure of the principal primary care domains. n METHODS The study participants were randomly selected from patients in a health maintenance organization group and a low-income group in South Carolina. They were either surveyed or interviewed regarding the achievement of primary care. Reliability, validity, and scaling analyses were conducted to assess and validate the 9 scales representing core primary care subdomains and 3 derivative domains: first contact accessibility, first contactutilization (first contact domain), longitudinality interpersonal relationships (longitudinality domain), coordination of services (coordination domain), comprehensiveness services available, comprehensiveness services received (comprehensiveness domain), family centeredness, community orientation, and cultural competence (derivative domains). n RESUL TS The results indicate that the hypothesized scales for primary care have substantial reliability and validity, and the extracted factors explained 88.1% of the total variance in the item scores. All of the 5 scaling assumptions (item-convergent validity, item-discriminant validity, equal item variance, equal item scale correlation, and score reliability) were met, suggesting that these items may be used to represent the primary care scales and the scoring of these items may be summed without standardization or weighting. n CONCLUSIONS Psychometric assessment supported the integrity and general adequacy of the PCAT-AE for assessing the characteristics and quality of primary care for adults. The PCAT-AE can be used as a quality measurement tool that assesses the adequacy of primary care experience.