Stormwater monitoring is underway for an infiltration basin that receives runoff from a commercial office park in the City of Altamonte Springs, Florida. The 29,000 cubic foot infiltration basin receives runoff from the 6.9 acre watershed through an internal manhole weir that diverts water into the basin for manhole water depths less than five feet. Outflow from the infiltration basin is controlled by a second internal weir that allows overflow from the basin for water depths in excess of three feet. The monitoring program is providing data on water levels in the basin, and water quality data for any overflows from the infiltration basin to the Little Wekiva River. The water levels are continuously monitored using a Remote Data Systems WL-80, and outflow samples are collected hourly for the duration of the storm using an ISCO automatic sampler. The WL-80 data provides both surface water and groundwater elevations. The monitoring conducted from December 11, 1996 through August 14, 1997 indicates that the infiltration basin has stored all runoff from the watershed, except for the runoff on one date when there was two consecutive days where rainfall was approximately two-inches/day. Rainfall during the study period was 45.1 inches, and the maximum water depth in the infiltration basin was 3.05 feet. Monitoring will continue until December 1997 in accordance with requirements established by the East Central Florida Regional Planning Council.