To document the changes in runoff characteristics of basins subject to urbanization, streamflow and precipitation data were collected at eight small basins in Antelope Valley, California, for the period 1990-93. The data collected at U.S. Geological Survey stations were supplemented by data collected at 35 long-term precipitation stations. These data will be used to calibrate and verify rainfall-runoff models for the eight basins and for estimating basin runoff characteristics throughout Antelope Valley. Annual precipitation in Antelope Valley varies from more than 50 cm in the mountains to less than 10 cm on the valley floor. Most precipitation in the valley occurs during the winter months, December through March, but cyclonic storms in the fall and convectional storms in the summer sometimes occur.