The results of a 1999 national survey of the ambulatory care responsibilities of pharmacists in managed care organizations (MCOs) and integrated health systems are reported and compared with the results of a similar survey conducted in 1997. Four hundred MCOs and integrated health systems participated in the telephone survey. The survey elicited data about organizational structure and pharmacist functions in the ambulatory care environment. Survey recipients were asked about 24 specific ambulatory pharmacist functions. The performance of functions was related to five "enabling" factors: pharmacists on interdisciplinary teams, automated dispensing systems, integrated electronic medical records, and "very supportive" medical staff and senior management. Thirteen functions were reported to be routine activities for more than 50% of the respondents, compared with nine functions in 1997. The top four functions-using pharmacoeconomic data to make formulary decisions, conducting medication management programs, tracking adverse drug reactions, and providing written information with each new prescription-were performed in 75% or more of organizations. Some 15-18% of respondents indicated they would add specialized pharmacy-managed clinics, services to determine patient use of herbal products and dietary supplements, and Internet prescription services within 12 months, suggesting this expansion is likely to continue. Enabling factors supported expansion. Two clusters of functions were identified that related to either population-focused or patient-focused activities, and these were supported differentially by enabling factors. Group-model and staff-model HMOs had the most enabling factors and the greatest scope of pharmacist functions. Independent practice associations had fewer enabling factors and a different mix of pharmacist functions, with an emphasis on population-focused functions, suggesting that a second model of ambulatory care pharmacist activity may be emerging. Ambulatory care functions of pharmacists in integrated health-system settings have expanded broadly since 1997.