Tetratogenesis, acute and chronic toxicity, and bioconcentration were investigated in various like stages of African clawed frogs (Xenopus laevis), bullfrogs (Rana catesbeiana) and leopard frogs (Rana pipiens) exposed to aqueous dieldrin in static-renewal and continuous-flow tests. Tadpole 96-hr LC50s ranged from 40.4 to 49.5 microgram/L for Xenopus, from 8.7 to 30.3 microgram/L for bullfrogs and was 71.3 microgram/L for leopard frogs. The 24-day LC50 for Xenopus tadpoles was 5.5 microgram/L; the 28-day LC50 for leopard frog tadpoles was 8.3 microgram/L. Adult leopard frogs had a 28-day LC50 of 53.4 microgram/L. Terata in Xenopus embryo-larval tests occurred at concentrations as low as 1.3 microgram/L after 10 days. Mean steady-state bioconcentration factors (BCF) for tadpoles ranged from 430 for Xenopus and from 540 to 1,130 for leopard frogs. Mean steady-state BCFs for adult leopard frog skin, muscle and liver ranged from 40 to 310. Existing dieldrin water quality criteria values appear to protect frogs. The relative similarity of response of the frogs to dieldrin demonstrates the usefulness of Xenopus in assessing potential environmental hazards.