This research assessed the occurrence of hydroxylated atrazine degradation products (HADPs) in streamwater from Goodwater Creek watershed in the claypan soil region of northeastern Missouri. Streamwater was sampled weekly from June, 1992 to December, 1994 at a V-notch weir used to measure streamflow for this 7250-ha watershed. Filtered water samples were prepared by cation exchange solid-phase extraction and analyzed for hydroxyatrazine (HA), deethylhydroxyatrazine (DEHA), and deisopropylhydroxyatrazine (DIHA) by high performance liquid chromatography with UV detection. HADPs were confirmed by electrospray HPLC/MS/MS and direct probe MS methods. Frequency of HADP detection was 100% for HA, 25% for DEHA, and 6% for DIHA. Concentrations ranged from 0.18-5.7 μg L -1 for HA, <0.12-1.9 μg L -1 for DEHA, and <0.12-0.72 μg L -1 for DIHA. These results establish that HADPs can contaminate surface water and that HA contamination of surface water is a significant fate pathway for atrazine in this watershed.