After detection of perfluorooctanoic acid (PFOA) in two New Jersey (NJ) public water systems (PWS) at concentrations up to 0.19 μg/L, a study of PFOA in 23 other NJ PWS was conducted in 2006. PFOA was detected in 15 (65%) of the systems at concentrations ranging from 0.005 to 0.039 μg/L. To assess the significance of these data, the contribution of drinking water to human exposure to PFOA was evaluated, and a health-based drinking water concentration protective for lifetime exposure of 0.04 μg/L was developed through a risk assessment approach. Both the exposure assessment and the health-based drinking water concentrations are based on the previously reported 100:1 ratio between the concentration of PFOA in serum and drinking water in a community with highly contaminated drinking water. The applicability of this ratio to lower drinking water concentrations was confirmed using data on serum levels and water concentrations from other communities. The health-based concentration is based on toxicological end points identified by U.S. Environmental Protection Agency (USEPA) in its 2005 draft risk assessment. Recent information on PFOA’s toxicity not considered in the USEPA risk assessment further supports the health-based concentration of 0.04 μg/L. In additional sampling of 18 PWS in 2007−2008, PFOA in most systems was below the health-based concentration. However, PFOA was detected above the health-based concentration in five systems, including one not previously sampled.