The private provision of health services in Vietnam was legalized in 1989 as one of the country's means to mobilize resources and improve efficiency in the health system. Ten years after its legalization, the private sector has widely expanded its activities and become an important provider of health services for the Vietnamese people. However, little is known about its contribution to the overall objectives of the health system in Vietnam. This paper assesses the role of the private health care provider by examining utilization patterns and financial burden for households of private, as compared with public, services. We found that the private sector provided 60% of all outpatient contacts in Vietnam. There was no difference by education, sex or place of residence in the use of private ambulatory health care. Although there was evidence suggesting that rich people use private care more than the poor, this finding was not consistent across all income groups. The private sector served young children in particular. Also, people in households with several sick members at the same time relied more on private than public care, while those with severe illnesses tended to use less private care than public. The financial burden for households from private health care services was roughly a half of that imposed by the public providers. Expenditure on drugs accounted for a substantial percentage of household expenditure in general and health care expenditure in particular. These findings call for a prompt recognition of the private sector as a key player in Vietnam's health system. Health system policies should mobilize positive private sector contributions to health system goals where possible and reduce the negative effects of private provision development.