Solid-phase extraction techniques were evaluated for the extraction of P-agomsts from biological matrices prior to determination by radioimmunoassay. Clenbuterol was extracted from aqueous liver homogenates using a combmation of on-column liquid/liquid partitioning coupled to a silica sohd-phase extraction step following initial enzymatic digestion of the liver sample. The procedure was validated at fortification levels of 0 2 and 0 4 ppb clenbuterol Recovery of clenbuterol was greater than 60% at both concentrations. Four P-agomsts were extracted from bovine unne and liver samples using mixed-mode sohd-phase extraction columns. The procedure was validated for clenbuterol, mabuterol, salbutamol and terbutalme at levels of 2 and 5 ppb. The mean recovery for the P-agomsts from liver and unne was greater than 75% and 85%, respectively. The limit of detection was 0 13 ng/ml and 0 46 ng/g of clenbuterol in unne and liver, respectively. Clenbuterol and salbutamol were extracted from bovine liver samples using a mixed-mode matnx sohd-phase dispersion/ion exchange procedure. Four types of sorbent were mvestigated m order to determine which sorbent combined most effectively with the ion exchange matenal in retaining the P-agomsts Recovery of clenbuterol and salbutamol from liver samples fortified at 50 ppb was greater than 80%, the resulting extracts were insufficiently punfied to allow for determination of Pagomsts at low or sub-ppb levels An enzymatic hydrolysis step was required for the determination of conjugated residues of salbutamol m incurred liver samples.