Of 149 patients with suspected cytomegalovirus (CMV) gastrointestinal disease, 51 (36%) confirmed cases, 6 (4%) probable cases, and 64 (45%) instances of non-CMV gastrointestinal disease were analyzed using the CMV antigenemia assay; 22 patients (5%) with indeterminate gastrointestinal disease were excluded. The sensitivity and specificity of the CMV antigenemia assay (defined as detection of > or =1 positive cells per 200,000 leukocytes) for diagnosis of CMV gastrointestinal disease were 54% (95% confidence interval, 41%-68%) and 88% (95% confidence interval, 77%-94%), respectively.