1 This study on 21 neurosurgical patients was set up to investigate the extent to which four chronically administered beta‐adrenoceptor blockers, propranolol, oxprenolol, metoprolol and atenolol, cross and blood‐brain barrier and enter the cerebrospinal fluid (CSF) and brain tissue. The concentration in the CSF of the three lipophilic beta‐ adrenoceptor blockers, propranolol, oxprenolol and metoprolol, approximated to the free drug concentration in the plasma, and was a poor predictor of brain concentration. These three lipophilic beta‐ adrenoceptor blockers appeared in brain tissue at concentrations 10‐20 times greater than that of hydrophilic atenolol. The approximate brain/plasma ratio for propranolol was 26, for oxprenolol 50, for metoprolol 12 and for atenolol 0.2. 2 The low concentration of atenolol in brain tissue is possibly responsible for the low incidence of central nervous system‐related side effects in patients on this agent compared to lipophilic beta‐adrenoceptor blockers.