The chicken embryo, brine shrimp(Artemia salina)and selected bacteria(Staphylo‐coccus epidermidis, Micrococcus flavus, andBacillus subtilis)were evaluated as alternative test systems for the determination of paralytic shellfish poisoning toxicity (saxitoxin). Dose levels ranging from 0.045 to 0.3 \ig were administered to the developing embryo through the air cell at either 0 or96h following incubation. Embryos dosed96h after incubation were the most sensitive, with 100% mortality at the 0.11‐μgdose level 24 h following exposure. Embryo mortality was 42% at to 0.3‐μg dose level when the toxin was administered at 0 h. Some embryonic malformations were observed in the 0‐h treatment group. Brine‐shrimp larvae were sensitive to saxitoxin at a dose level of5μg. A dose response based on mortality was apparent only 48 h after dosing. Limited growth inhibition was observed with the bacteria tested at concentrations between 0.0035 and 0.35 μglwell.