Striped bass (Morone saxatilis) appear to be a desirable test species for the estuarine environment because their critical life stages are spent in estuaries, they have wide tolerance to salinity, and they are available through government and private hatcheries. Toxicity test procedures and life stage sensitivity were evaluated based upon results from acute (96-h) and chronic (36-d) larvae-to-fry and (45-d) embryos-to-fry tests. Replicate tests with molinate, thiobencarb, and endosulfan resulted in coefficients of variation for 96-h LC50 values of less than 30%. Striped bass larvae were more sensitive to several pesticides than chinook salmon (Oncorhynchus ishawytscha) fry. Lower 96-h LC50 (micrograms/L) values were obtained using striped bass larvae compared to chinook salmon fry for a variety of pesticides including carbofuran (210 versus 610), thiobencarb (730 versus 760), molinate (9400 versus 13,000), endosulfan (0.31 versus 0.74), and malathion (47 versus 101). Striped bass larvae-to-fry and chinook salmon embryos-to-fry had similar sensitivity to molinate and to thiobencarb; MATC values ((NOEC X LOEC)(sup 1/2)) were 290 and 170 micrograms/L molinate and < 27 to 73 and 37 micrograms/L thiobencarb, respectively.