Procedures are described for optimising and validating an ELISA method for measuring clenbuterol residues in bovine liver without prior sample enrichment. Optimal assay conditions are obtained by preincubating liver supernatant with an immobilised antibody raised to clenbuterol-ovalbumen. After further incubation with a salbutamol-peroxidase conjugate, colour is developed using a tetramethylbenzidene substrate. The assay will permit measurement of clenbuterol residues in liver at the maximum residue level of 0.5 ng g-1 with a confidence of > 99%.