Titanium dioxide (TiO2) photocatalysis has been used to initiate the destruction of nodularin, a natural hepatotoxin produced by cyanobacteria. The destruction process was monitored using liquid chromatography-mass spectrometry analysis which has also enabled the identification of a number of the photocatalytic decomposition products. The reduction in toxicity following photocatalytic treatment was evaluated using protein phosphatase inhibition assay, which demonstrated that the destruction of nodularin was paralleled by an elimination of toxicity. (c) 2005 Elsevier B.V. All rights reserved.