Fluid overload is not infrequent in continuous ambulatory peritoneal dialysis (CAPD) patients. In our experience, extemporaneous continuous venous-venous hemofiltration (CVVHF) was able to correct fluid imbalances refractory to high dose diuretics and hypertonic solutions. We treated 8 of 52 patients (5 females, 3 males, mean age 52 years) on CAPD from 4 to 36 months and with fluid overloads of up to 10 kg. A Biospal SCU/CAVH flat-sheet high-flux hemodialyzer employed for 10 h produced an ultrafiltration rate (QB:150 ml/min) of 11.12 +/- 4.97 ml/min. With an isotonic replacement solution, the filter provided sufficient extraction of small molecules so that CAPD could be interrupted during CVVHF. The procedure appeared well tolerated. This approach reduced the use of hypertonic dialysate, which is not devoid of side effects on ultrafiltration capacity of the peritoneal membrane.