The disposition of famotidine was evaluated in 18 patients; Group 1, mild renal insufficiency, [creatinine clearance (CLCR): 30–60 mL/min]; Group 2, moderate to severe renal insufficiency (CLCR: 10–30 mL/min); Group 3, end‐stage renal disease requiring maintenance hemodialysis (anuric). Blood and urine samples were obtained over a 72‐hour period. Plasma concentration‐time data demonstrated biexponential decay. The terminal elimination half‐life was prolonged in Group 3 (18.6 ± 5.7 hr) compared with Groups 1 (9.3 ± 2.3 hr) and 2 (9.7 ± 1.7 hr), P < .05. Steady‐state volume of distribution ranged from 0.80 to 1.26 L/kg but did not differ among the groups. Total body clearance (CLP) and renal clearance were significantly lower in Groups 2 and 3 patients compared with Group 1 patients. Nonrenal clearance was not related to CLCR. The CLP correlated well with CLCR (CLP = 1.59 CLCR + 33.8, r = 0.830, P < .05). These data indicate that dosage adjustment may be necessary in patients who have renal insufficiency.