Perfluorooctanesulphonicacid (PFOS), a persistent organic contaminant, has been widely detected in the environment, wildlife and humans, but few studies have assessed its effect on aquatic organisms. The present study evaluated the effect of PFOS on zebrafish embryos. Zebrafish embryos exhibited developmental toxicity of bent spine, uninflated swim bladder, decreased heart rate and affected spontaneous movement after exposure to various PFOS concentrations (0-8mg/L) from 6 to 120h post-fertilization (hpf). The LC(50) at 120hpf was 2.20mg/L and the EC(50) at 120hpf was 1.12mg/L. Continuous exposure to PFOS from 1 to 121hpf resulted in a steady accumulation with no evidence of elimination. PFOS induced cell death at 24hpf was consistently found in the brain, eye, and tail region of embryos. PFOS exposure induced lesions in the muscle fibers with histological examination. Behavior assessment of PFOS in zebrafish embryos elevated the basal rate of swimming after 4 days of exposure, and larvae exposed to PFOS (0.25-4mg/L) for only 1h at 6dpf swam faster with increasing PFOS concentration. Embryos/larvae exposed to 8mg/L PFOS for 24h periods from 1 to 121hpf showed the highest incidence of malformations in the 97-121hpf window. This is the first study to define uptake kinetics and to focus on behavioral consequences following PFOS exposure in zebrafish. Our results further the understanding of the toxicity of PFOS to aquatic organisms and suggest the need for additional research to identify the mode of PFOS toxicity.