We optimized conditions for liquid chromatography-mass spectrometric analysis for the following ten representative toxins associated with diarrhetic shellfish poisoning: okadaic acid (OA), dinophysistoxin-1 (DTX1), 7-O-palmitoyl-OA, 7-O-palmitoyl-DTX1, pectenotoxin-1, -2, and -6, pectenotoxin-2 seco acid, yessotoxin (YTX), and 45-hydroxy-YTX. Emphasis was laid on securing good recoveries during clean-up steps. Toxins in the hepatopancreas of scallops (2g) were extracted with 90% methanol, transferred to chloroform by partition, and treated on a Sep-pak silica cartridge with acetone/methanol. Good recoveries were obtained except for 45-hydroxy-YTX, which was difficult to extract with chloroform by partition and thus was treated on a buffered Sep-pak C18 cartridge. [M-H]- ions were selected for monitoring carboxylic toxins, [M+Na]+ ions for PTX1 and PTX2, and [M-Na]- ions for YTXs. The method suites not only monitoring but also toxin accumulation and depuration studies.