From 1978 to 1989, 4,772 endoscopic cytological examinations of the stomach have been done in our laboratory, including 903 patients with a final diagnosis of gastric carcinoma. There were seven false-positive results among 3,810 examinations done in patients without malignant disease (specificity 99.8%). Cytology yielded positive results in 785 of 903 carcinomas (sensitivity 86.9%), while biopsies were positive in 826 of 895 cases (sensitivity 92.3%). Both techniques combined resulted in positive diagnoses in 886 of 903 malignancies (sensitivity 98.1%). Cytology was positive in 52 patients with negative biopsies as well as in eight patients in whom biopsies had not been obtained. Thus cytology added 60 positive diagnoses (6.7%) to the overall diagnostic results. These results suggest that endoscopic cytology is useful for avoiding unnecessary delays caused by having to perform repeated endoscopic biopsies. It should be done as a routine procedure in those institutions in which significant numbers of gastric carcinomas are studied and where an experienced gastrointestinal cytology laboratory is available.