1 Rectus abdominis muscle biopsies were obtained from 28 patients undergoing abdominal surgery. In membranes prepared from these biopsies ,-adrenoceptor binding was examined. The apparent affinity (KD) and the density (Bmax) of the receptors for the radioligand (_)_[1251 cyanopindolol were 28.5 ± 2.7 (pM) and 25.9 ± 2.1 (fmol mg-, protein) (mean ± s.e. mean) respectively. In forceps biopsies from vastus lateralis muscle from four healthy volunteers the values for KD and Bmax were 22.5 ± 4.4 (pM) and 16.4 ± 2.2 (fmol mg-' protein). The binding characteristics for the radioligand were similar in the biopsies from the two muscle sites.2 Inhibition of the radioligand binding by the selective P2-adrenoceptor antagonist ICI 118551 (KI = 117 ± 45 nM) and selective 131-adrenoceptor antagonist metoprolol (K1 = 15229 ± 5046 nM) suggests the dominance of 132-adrenoceptor subtype in human skeletal muscle. 3 There were no significant differences in the skeletal muscle ,-adrenoceptor densities or affinities between the young and older patients.