Larval topsmelt (Atherinops affinis) and inland silversides (Menidia beryllina) were exposed in 96-hr static acute toxicity tests to eleven chemicals to determine the relative sensitivity of the two atherinid species. High to low LC50 ratios for endosulfan, methoxychlor, carbophenothion, chlorpyrifos, terbufos, fenvalerate, permethrin, 4-nitrophenol, and sodium lauryl sulfate were within a factor of <2 for the two species. A. affinis was more sensitive to both azinphos-methyl and 2,4-dinitrophenol by factors of 6.7 and 4.4, respectively. Comparison of the relative sensitivity of A. affinis with three freshwater fish species (Lepomis macrochirus, Oncorhynchus mykiss, Pimephales promelas) and one estuarine fish species (Cyprinodon variegatus) are also presented. Sensitivities were similar between A. affinis and the two most sensitive freshwater species, L. macrochirus and O. mykiss. A. affinis is easily transported, cultured and maintained in the laboratory, and readily adaptable for use in toxicological studies.