The pharmacokinetics of sulphamethizole, paracetamol and phenylbutazone were investigated and compared in young and geriatric subjects. The rate and extent of absorption of the drugs did not appear to be affected by increasing subject age. However, the mean half-lives for sulphamethizole and paracetamol were significantly increased in the geriatric subjects. A number of correlations are presented between the elimination rate constants of the drugs and certain subject parameters and variables. The elimination of phenylbutazone was found not to be influenced significantly by subject age. The apparent volumes of distribution of the three drugs were not age-dependent.