Several earlier studies compared performance differences between USMGs and FMGs in inpatient care settings, mainly hospitals. This study compares performance differences between USMGs and FMGs in ambulatory care settings. The sample consisted of 14,203 patient episodes treated by 1,156 physicians (pediatricians, obstetricians/gynecologists, internists, and other specialty physicians). The study setting was a midwestern state. Little evidence was found to support the hypothesis that the medical school origin (U.S. and foreign) had influenced physicians' technical quality in practice. Mean differences between the USMGs and FMGs were either not significant or contrary to the general assumption. The FMGs provided equal care to the USMGs, and sometimes the FMGs provided even marginally better care than the USMGs.