Campus parking lot stormwater (CPLSW) runoff can mobilize a variety of constituents from vehicular and atmospheric deposition that may pose risks to receiving aquatic systems. The objective of this study was to characterize CPLSW and to discern potential constituents of concern that may affect aquatic biota in receiving systems. Characterization of CPLSW included analyses of metals, oil and grease, and general water chemistry. Toxicity tests were performed using two sentinel species, Ceriodaphniadubia Richard and Pimephales promelas Rafinesque. Metals measured (at their maximum) in CPLSW included 4756microg Al L(-1), 53microg Cu L(-1), 130microg Pb L(-1), and 908microg Zn L(-1). Although CPLSW varied widely in composition and toxicity, constituents of concern included: pH, alkalinity, total suspended solids, biological oxygen demand, chemical oxygen demand, metals, and oil and grease. Fish (P. promelas) were more sensitive to CPLSW than C. dubia with decreased survival in 92% and 15% of the samples (n=13), respectively.