Small water enterprises (SWEs) are water delivery operations that predominantly provide water at the community level. SWEs operate beyond the reach of piped water systems, selling water to households throughout the world. Their ubiquity in the developing world and access to vulnerable populations suggests that these small-scale water vendors may prove valuable in improving potable water availability. This paper assesses the current literature on SWEs to evaluate previous studies and determine gaps in the evidence base. Piped systems and point-of-use products were not included in this assessment. Results indicate that SWES are active in urban, peri-urban and rural areas of Africa, Asia and Latin America. Benefits of SWEs include: no upfront connection fees; demand-driven and flexible to local conditions; and service to large populations without high costs of utility infrastructure. Disadvantages of SWEs include: higher charges for water per unit of volume compared with infrastructure-based utilities; lack of regulation; operation often outside legal structures; no water quality monitoring; increased potential for conflict with local utilities; and potential for extortion by local officials. No rigorous, evidence-based, peer-reviewed scientific studies that control for confounders examining the effectiveness of SWEs in providing potable water were identified.