We prospectively evaluated the efficacy in 100 patients of two effervescent contrast agents commonly used in routine double-contrast upper gastrointestinal (GI) tract examinations: Baros and E-Z-Gas II granules. The study was double blinded. Two radiologists, who were not aware of which effervescent agent was being used, objectively evaluated the radiographic studies. Patient ease in swallowing and acceptance of the effervescent granules was 94% for Baros and 68% for E-Z-Gas II granules. The objective evaluation of the radiographs showed adequate gastric distension (Baros, 94%; E-Z-Gas II, 90%) and adequate to excellent mucosal coating for both agents (Baros, 92%, E-Z-Gas II, 94%). Areae gastricae were better seen with Baros (64% vs. 30%), and air bubbles were less of a problem with Baros. We conclude that Baros effervescent granules have certain distinct advantages over E-Z-Gas II granules regarding patient tolerance and acceptance, better visualization of the areae gastricae, and less degradation of the quality of the radiographs by air bubbles. The differences in mucosal coatings for the two agents was insignificant.