We studied theophylline elimination in 8 patients with chronic renal failure to determine the effect of hemodialysis on the pharmacokinetics of theophylline. Each subject was studied twice, once on a nondialysis day and again during dialysis. Total body theophylline clearance on the nondialysis day was similar to that reported for patients with normal renal function (57–4 ± 27.2 ml/kg/h). Hemodialysis accelerated theophylline elimination and shortened serum theophylline half-life in all patients (nondialysis t½ = 7.3 h ± 2.3 vs. dialysis t½ = 2.7 ± 0.9 h, p < 0.01). Dialysis clearance averaged 59.7 ± 16.4 ml/kg/h with a fraction of drug removed of 0.4 liters in 4 h. Guidelines for theophylline management during hemodialysis are suggested.