The repellent ethyl hexanediol (2-ethyl-1,3-hexanediol) was tested against the mosquito Aedes dorsalis in a coastal salt marsh in California. The experimental design incorporated a linear regression model, sequential treatments and a proportional end point (95%) for protection time. The protection time of 0.10 mg/cm2 ethyl hexanediol was estimated at 0.8 h. This time is shorter than that obtained previously for deet (N,N-diethyl-3-methylbenzamide) against Ae. dorsalis (4.4 h).