The bioavailability of a single 250-mg oral dose of tetracycline hydrochloride was studied in seven patients following Billroth-II gastrectomy in comparison with seven control subjects matched for age and body weight. There were no significance differences between control subjects and gastrectomized patients in the apparent lag time prior to the start of absorption (23.6 vs. 22.8 min), peak serum tetracycline concentration (1.72 vs. 1.75 microgram/ml), the time of attainment of peak concentrations (3.35 vs. 3.42 hr), the apparent first-order absorption half-life (1.8 vs. 1.4 hr), or the apparent first-order elimination half-life (8.0 vs. 8.7 hr). Completeness of tetracycline absorption, as judged by area under the 24-hr serum concentration curve, did not differ significantly between the two groups, nor did 24-hr urinary excretion of tetracycline. Thus the abnormalities of gastrointestinal structure and function produced by Billroth-II gastrectomy do not result in impairment of the rate and completeness of tetracycline absorption.