A simple and sensitive method for the analysis of ivermectin (22,23-dihydroavermectin B1) in swine liver based on immunoaffinity column cleanup is described. The immunosorbent was prepared by coupling polyclonal anti-ivermectin antibodies to carbonyl diimidazole-activated Sepharose CL-4B. After extraction with methanol, ivermectin was cleaned up on an immunoaffinity column, and determined by reversed-phase liquid chromatography with UV absorbance detection at 245 nm. Recoveries of ivermectin from fortified samples of 5-10 micrograms kg-1 levels ranged 85-102%, with coefficients of variation of 6-12%. The limit of detection was 2 micrograms kg-1 in a 5-g samples.