To better assess the construction, maintenance, and function of the Kock ileal urinary reservoir with its continent antirefluxing nipple valves, laboratory investigations in dogs were done simultaneously with clinical trials in humans in 1983. Fifteen dogs underwent creation of hemi-Kock ileal reservoirs (without the efferent valve and limb) that were anastomosed to their bladders as enterocystoplasties. The afferent antirefluxing nipple valves were intussuscepted after 7 cm of underlying mesentery had been removed. The nipples were further stabilized with metal and absorbable (Polysorb) staples and Marlex collars. The right ureters were anastomosed to the afferent limb of the reservoirs with the contralateral systems left intact as controls. Ten dogs were able to be followed at the vivaria for twelve to thirty-six months and then studied. All nipple valves remained intact, viable, and nonrefluxing without revision. All kidneys remained histologically normal except those in dogs with dilated ureters secondary to ureteroileal stenosis with concurrent calculi formation. Calculi formed on exposed metal staples and Marlex. The absorbable staples were found to promote appropriate healing and were never the nidus for stone formation. It appears that the intussuscepted nipple valve (with its mesentery removed) is reproducible and functionally reliable in preventing reflux. It also appears these valves can histologically preserve diverted kidneys if the upper urinary tract drainage is normal and calculi are minimized. The proper placement of staples and the elimination of Marlex-anchoring collars are indicated to minimize calculi.