To the editor: We wish to point out a potential hazard incurred with gentamicin therapy not addressed in the review article on gentamicin by Appel and Neu in the October 1978 issue (1). Concentrations of antibiotics in ascitic fluid have been shown to be adequate in patients with bacterial peritonitis who receive systemic therapy (2, 3). Because information on transperitoneal movement of antibiotics is limited, drug dosage and route of administration in such patients are usually chosen empirically. The following case presents an unusual gentamicin dosing problem. A 63.2-kg 45-year-old black man with a long history of alcohol abuse presented