From October 2002 to April 2004, data were collected from Dallas/Fort Worth (DFW) International Airport (TX, USA) outfalls and receiving waters (Trigg Lake and Big Bear Creek) to document the magnitude and potential effects of aircraft deicer and anti-icer fluid (ADAF) runoff on water quality. Glycol concentrations at outfalls ranged from less than 18 to 23,800 mg/L, whereas concentrations in Big Bear Creek were less because of dilution, dispersion, and degradation, ranging from less than 18 to 230 mg/L. Annual loading results indicate that 10 and 35% of what was applied to aircraft was discharged to Big Bear Creek in 2003 and 2004, respectively. Glycol that entered Trigg Lake was diluted and degraded before reaching the lake outlet. Dissolved oxygen (DO) concentrations at airport outfalls sometimes were low (5.0 mg/L). Results of toxicity tests indicate that effects on Ceriodaphnia dubia, Pimephales promelas, and Selanastrum capricornutum are influenced by type IV ADAF (anti-icer), not just type I ADAF (deicer) as is more commonly assumed. ?? 2006 SETAC.