Background: Currently, ultraflitration during peritoneal dialysis is determined from direct measurement of weight differences between the initial filling and final draining volumes. A new technique based on segmental bioimpedance analysis (SBIA) has been developed to accurately measure intraperitoneal volume continuously during peritoneal dialysis. Methods: Twenty-two peritopeal dialysis patients were studied in a supine position during peritoneal dialysis consisting of 4 tidal exchanges (TPD). For bioimpedance measurements, 4 electrodes were placed, 1 on each hand and foot, to inject an alternating current. Sensing electrodes were placed on the lower ribs and the buttocks on both sides of the body. Calibration of the SBIA method was performed by first filling a known volume of dialysate to establish the relationship between change in resistance and a known fluid volume in the peritoneal cavity. The increase of fluid volume in the peritoneal cavity during dwell time was considered to be equal to net ultrafiltration volume occurring during this period. These measurements were compared with those obtained by the difference in weight between the total filling and draining volumes. Results: The change in intraperitoneal volumes measured by differences in weight (0.39 ± 0.29 L) did not differ significantly from those established from SBIA (0.41 ± 0.31 L). Bland-Altman analysis yielded limits of agreement of 0.12 L. Conclusion: The SBIA technique provides a continuous noninvasive approach to the measurement of changes in intraperitoneal fluid volume.