Endoscopic injection sclerosis is a therapeutic alternative in the management of esophageal varices. Complications of sclerotherapy have been minor, including fever, bacteremia, and abnormal chest x-ray. We performed a prospective study to evaluate the frequency of postsclerosis bacteremia. Bacteremia was detected in 14 procedures (50%). There were no cases of bacteremia in a group of control patients with esophageal varices undergoing upper gastrointestinal endoscopy without sclerosis (p less than 0.05). Bacteremia was transient and unrelated to the presence of fever or other clinical complications. The organism most commonly cultured from blood, alpha-hemolytic streptococcus, probably represents a contaminant from the oropharynx, introduced into the bloodstream during sclerosis. We conclude that injection sclerotherapy of esophageal varices is associated with a higher incidence of bacteremia than routine upper endoscopy and that selected patients may require antibiotic prophylaxis when undergoing this procedure.