We report two patients with portal hypertension secondary to cystic fibrosis who developed transient gross hematuria following injection sclerotherapy of esophageal varices. Both patients developed this complication within 6 h of sclerosing sessions during which sodium morrhuate was used. Each cleared her hematuria within 4 days without developing oliguric renal insufficiency. Subsequent sclerotherapy was associated with no untoward effects. These are the only two pediatric patients among 40 whose varices we have sclerosed who have developed gross hematuria at the time of sclerotherapy, and they are our only two patients undergoing sclerotherapy who have had cystic fibrosis. The factors rendering them vulnerable to renal or urinary tract insult in the absence of other systemic complications are unclear. However, the therapeutic endoscopist should be cognizant of this potential adverse reaction when performing sclerotherapy.