Periphyton was collected from artificial substrates placed in the Sacramento and Feather rivers, California, and analyzed to determine the rate of colonization and succession of periphyton types with time. Samples for determination of water-quality characteristics, especially suspended-sediment concentrations, that might have a direct effect on the growth of periphyton were collected during each station visit. This paper describes the methods of data collection and presents qualitative and quantitative findings of periphyton collected during two colonization periods (August 5-September 5, 1975, and November 28-December 29, 1975) and associated water-quality data.