A liquid chromatographic-atmospheric pressure ionization ion spray method for the determination of anatoxin-a, microcystin desmethyl-3, LR, RR, and YR in fish muscle, is described. A salmon muscle sample was extracted with a mixture of methanol-water and acetone. The organic layer was evaporated and cleaned-up using LMS solid phase extraction columns. The method is simple, specific, and requires only small quantities of chemical reagents. The lower limits of quantification were 15, 2, 10, 1, and 10 ng/g for anatoksin-a, microcystin desmethyl-3, LR, RR, and YR, respectively.