Reproducibility of the so-called "mucolytic effect" of the 2%-10% dextrose-water solution is questioned. To test the mucolytic effect of 5% and 10% dextrose-water solutions and to determine what could be a true mucolytic agent, in vitro and in vivo studies were undertaken in two proven pseudomyxoma peritonei cases. In vitro study: Immediately after the mucin jelly was taken out of the peritoneal cavity, the jelly was immersed in various 40 cc solutions including: 1) 5% dextrose-water; 2) 10% dextrose-water; 3) normal saline; 4) lactated Ringer; 5) distilled water. The mucolytic effects of these solutions were observed once every hour after vigorous mixing. In vivo study: After completion of the operation, the peritoneal cavity was repeatedly irrigated with massive warm 5% dextrose-water and normal saline solutions in an attempt to dissolve the residual mucin cake and jelly. Neither 5% and 10% dextrose-water solution nor control solutions of normal saline, lactated Ringer, and distilled water could dissolve the mucin jelly in test tubes at 0, 1, 2, and 3 hours. The "claimed" mucolytic agent, 5% dextrose-water solution could not facilitate the removal of both mucin jelly and cake in the peritoneal cavity. The 5% dextrose-water solution was not superior to the normal saline solution in terms of mucolytic effect. In the present study, a true mucolytic agent does not exist. Currently, multiple laparotomy for aggressive cytoreduction remains the treatment of choice for pseudomyxoma peritonei.