This paper pinpoints important differences within the private sector in Vietnam. It shows that the country's private sector is much more heterogeneous than is often suggested, and attempts to reveal some of the causal mechanisms that cause this diversification. Theoretically, the paper draws on business system theory, particularly on that aspect of it that deals with internal business organisation, in order to examine the nature of and trends in relation to firm-level management and control. On this background, the paper uncovers a Vietnamese-owned segment in Hanoi, two different Vietnamese-owned segments in Ho Chi Minh City distinguished by the origins of their owners, and a Vietnamese Chinese-owned segment in Ho Chi Minh City.