Three methods of paraquat analysis have been examined and a suitable procedure for clinical laboratory use is recommended. The method is rapid and can determine down to 0.01 μg paraquation/ml in a 250-ml aliquot of urine. A rapid spot test with visual sensitivity of 1–1.5 μg ion/ml is also described. Some urine levels following oral ingestion of paraquat are reported, but it was not possible to correlate the levels found with severity of poisoning.