This report presents analyses of low-flow data for 12 continuous-record streamflow gaging stations and 81 partial-record sites in eastern Puerto Rico. Information on low-flow magnitude and frequency is essential in hydrologic studies and for optimum development of surface water resources. The report includes analyses of low-flow data and tabulations of computed low-flow magnitude and frequency for 7, 14, 30, 60, and 90 consecutive days with recurrence intervals of 2 and 10 years for continuous-record gaging stations. Low-flow estimates are provided for partial-record stations for 7, 14, and 30 consecutive days with recurrence intervals of 2 and 10 years. Values at partial-record stations were estimated from the relation between concurrent flows at the partial-record stations and nearby continuous-record stations.