This article investigates whether there are efficiency costs associated with the pronounced rightward skew in the firm size distribution, or Vietnam's 'missing small and medium size enterprise (SMEs)', drawing on panel data analysis of firm growth and survival. Specifically, it examines if factor allocation biases with respect to credit, preferable treatment of state owned enterprises, barriers to entry into export markets and economies of scale are important determinants of growth rates and survival probabilities of small, medium and large-sized firms. Overall, findings on the earlier variables do not support the view that there are large efficiency costs associated with Vietnam's 'missing SMEs'. Together with other results in the literature with do not find significant equity costs associated with Vietnam's 'missing SMES', these findings raise questions about policy initiatives in support of SMEs in Vietnam, such as the National SME Support program, in particular, through improved access to credit.