Nadolol protein binding was measured in serum from 95 healthy subjects. Binding was found to range between 4 and 27%, with a mean of 14 +/- 4% (s.d.). There was a small but significant correlation found between the degree of nadolol binding and the serum alpha-1-acid glycoprotein concentration. However it was concluded that changes in the serum protein binding of nadolol were unlikely to give rise to any untoward clinical effects.