We collected 24 intact LapSacs* during a laparoscopy course at our institution. Following laparoscopic nephrectomy or nephroureterectomy in a pig using high speed electrical tissue morcellation, the sacks were examined for perforation. When filled with water, 4 of the 24 LapSacs (16%) were found to have small perforations. The 20 remaining sacks were randomly divided into 3 groups of 6 and 2 sacks, although intact, were kept as substitutes to use if a trial with the study sacks could not be completed. Each group of 6 sacks was tested for permeability using 10 mg./ml. bovine serum albumin, 8 mg./ml. indigo carmine or 1 x 10(5)/ml. mouse bladder tumor cells. The results in the 18 tested sacks showed no dialysis of bovine serum albumin in the dialysate at 1, 3 and 18 hours, and no dialysis of indigo carmine at 0, 1, 2 and 3 hours. In 1 of 6 sacks tested with a mouse bladder tumor cell line a single cell was noted on the hemocytometer at 1 and 3 hours. The lack of an increasing concentration of cells at the 3-hour interval likely indicates that this represented contamination of the dialysate rather than ongoing leakage from a perforated sack in this case. We conclude that the LapSac, when properly used, remains impermeable throughout the morcellation process.