"An okadaic acid (OA) etiology has been demonstrated for most outbreaks of diarrhetic shellfish poisoning (DSP) in Europe, An isomer of OA, dinophysistoxin-2 (DTX-2), has recently been found in Irish waters and, in 1991 and 1994, was the major toxin during prolonged infestations in cultivated mussels (Mytilus edulis) along the south-west coast of Ireland. The OA class of DSP toxins have been analysed by HPLC using modified versions of three established fluorescent derivatisation methods. A ‘dual tag’ method for the confirmation of specific toxins has also been developed. Survey work has been carried out over the past four years on several mussel culturing areas in the south-west of Ireland. Results of seasonal, geographical, as well as horizontal and vertical variations in shellfish toxicity are reported. Evidence that there is a correlation between changes in temperature and subsequent appearance of high cell counts of Dinophysis acufa in the surface water column exists. The monitoring of oceanographic profiles may be useful in predicting future toxic events. Two commercially-available ELISA methods, designed to determine OA were examined for potential use in the analysis of samples containing both OA and DTX-2. Rapid DSP- screening of shellfish in Ireland and other European countries may thus be possible using ELISA. International collaborative studies have been undertaken on new DSP toxins, DTX-2 and DTX-2B, which have been isolated in our laboratoiy. The cytotoxic and protein phosphatase activity of DTX-2 is presented. Mass spectral data for these toxins using LC-ISP-MS, FIA-MS and negative-ion FAB MS/MS techniques is reported. Preliminary findings using ozonolysis for the detoxification of contaminated shellfish is also presented. The synthesis of a new fluorogenic reagent for the analysis of carboxylic acids by HPLC is described. The reagent was found to react readily with saturated fatty acids in aqueous solution, under mild reaction conditions. "