At 20% v/v PFW fertilization was inhibited by 25%. This concentration was equivalent 0.0721 mg lÿ1 total hydrocarbon (THC). In contrast, larval metamorphosis was more sensitive to this e.uent, with 98% metamorphosis inhibited at the same concentration. Crude oil WAF did not inhibit fertilization of gametes until dispersant was introduced. Dispersed oil was slightly more toxic to fertilization than dispersant alone, suggesting toxicity to that event may be additive. The minimum concentration of dispersed oil which inhibited fertilization was 0.0325 mg lÿ1 THC.