Storm event sampling was conducted at eight locations to compare the effects of storm events on protozoa occurrence and concentrations in a creek, river, and sewage treatment plant effluent. The occurrence and concentrations of Giardia and Cryptosporidium increased during storm events compared to stable flow periods. The protozoa concentrations typically increased by more than a factor of 10 during storm events. These increases suggest that overall loading to the watershed during storm events increase to such a point that dilution by increased stream flow will not reduce protozoa concentrations. Water quality and stream measurements during the study showed that flow, turbidity, fecal coliforms, and total coliforms correlated with protozoa concentrations. This observation suggests that these parameters may serve as indicators of periods of increased protozoa levels in the source water in the studied watershed areas. Storm event profiles were collected on various occasions to better determine the effects of hydrograph position on protozoa concentration. The recording of three different protozoa concentration profiles during three different events demonstrated the importance of combination of watershed characteristics and existing hydrological conditions on source water levels of protozoa. Includes 3 references, tables, figures.