The disposition of flecainide was studied in a 60-year-old, 92 kg man, who was being administered flecainide to control ventricular arrhythmias. The patient was also being treated with continuous ambulatory peritoneal dialysis (CAPD) for end-stage renal disease. The patient was given two single doses of 100 mg and 200 mg of flecainide 1 week apart. Serum, dialysate and urine samples were collected at appropriate times. Areas under the serum concentration-time curves were used to calculate total body clearance, renal clearance and CAPD clearance. The values obtained were 56.6 ml/min, 6.2 ml/min and 2.2 ml/min, respectively. The percentage of a given dose of flecainide removed in 24 h by residual renal function and by CAPD was 4.7% and 1.1% respectively. It is suggested that the dosage reduction required for patients taking flecainide during CAPD should be similar to that for patients with end-stage renal disease but not on dialysis. No dosage change is required during CAPD.