Paraquat is known to cause severe lung damage through pulmonary edema as its initial feature of toxicity. The purpose of this study was to investigate the toxicity of paraquat in rabbits intraperitoneally injected with 2 or 4 mg/kg/day of the herbicide for a period of 7 days. In the lung, prostaglandin levels of the intoxicated rabbits showed a significant increase in PGF2 alpha. This increase was dose dependent. However, a nonsignificant change in the 6-keto-PGF1 alpha was also observed. Plasma and serum levels of thromboxane-B2 were also significantly elevated but the levels of 6-keto-PGF1 alpha were affected nonsignificantly. The pathology of elevated levels of PGF2 alpha and TXB2 in the lung and blood, in response to paraquat toxicity, is discussed.