OBJECTIVE: To review and evaluate research on pharmaceutical services in community and ambulatory care pharmacy settings, specifically study designs and patient outcome measures, and to provide recommendations to improve future research on pharmaceutical services in community and ambulatory care pharmacy settings. DATA SOURCE: English-language articles were identified by searching MEDLINE (1966-December 1998) and International Pharmaceutical Abstracts (1970-December 1998), using a combination of search terms: pharmacist services, pharmacist interventions, community pharmacy, ambulatory care, primary care, and patient outcomes. Relevant studies were selected based on article abstracts. DATA EXTRACTION: From each relevant study, we extracted the study objectives, sample size, study period, study design, major tasks performed by pharmacists, and economic, clinical, and humanistic outcomes (ECHO). Results were tabulated separately for research on community pharmacy and ambulatory care pharmacy settings. RESULTS: We identified 95 relevant studies. Of these, 21 studies were conducted in community pharmacy settings and 74 in ambulatory care settings. Ten community pharmacy studies used prospective, single group, pretest/posttest, or posttest only designs; seven used prospective two or more group comparison designs; and four used randomized, controlled designs. Nine studies on community pharmacies measured clinical outcomes, two measured humanistic outcomes, and five measured economic outcomes. Four studies measured both clinical and humanistic outcomes and one measured humanistic and economic outcomes. No study measured all three ECHO variables. Twenty-three studies in ambulatory care settings used prospective or retrospective, single group, pretest/posttest or posttest only designs; 21 used prospective or retrospective two-or-more group comparison designs; and 30 used randomized, controlled designs. Thirty-six measured clinical outcomes, five measured humanistic outcomes, and 15 measured economic outcomes. Fifteen studies measured clinical and economic outcomes and three measured clinical and humanistic outcomes. CONCLUSIONS: Only 21 of 95 selected studies were conducted in community pharmacy settings and measured the impact of pharmaceutical services on patient outcomes. Few studies employed adequate research designs to control threats to internal and external validity. In order to obtain a comprehensive and accurate picture of the impact of pharmaceutical services on patient outcomes, an attempt must be made to measure all three ECHO variables while employing adequate research design.