This meta-analysis was an evaluation of patient outcomes of nurse practitioners (NPs) and nurse midwives (NMs), compared with those of physicians, in primary care. The sample included 38 NP and 15 NM studies. Thirty-three outcomes were analyzed. In studies that employed randomization to provider, greater patient compliance with treatment recommendations was shown with NPs than with physicians. In studies that controlled for patient risk in ways other than randomization, patient satisfaction and resolution of pathological conditions were greater for NP patients. NPs were equivalent to MDs on most other variables in controlled studies. In studies that controlled for patient risk, NMs used less technology and analgesia than did physicians in intrapartum care of obstetric patients. NMs achieved neonatal outcomes equivalent to those of physicians. Limitations in data from primary studies precluded answering questions of why and under what conditions these outcomes apply and whether these services are cost-effective.