The authors used Toluidine Blue to stain gastric lesions in nine patients. Six cases were found with adenocarcinoma that stained an intense blue that was limited to the extension of the malignancy itself. The other three cases did not stain and their histological diagnosis had been benign chronic gastric ulcers. One patient did color faintly due to atypical cells in the ulcer crater. The authors concluded that it is a procedure easy to apply, simple, harmless, and inexpensive, that gives results and permit the differentiation of malignant lesions from benign ones. They therefore recommend the method to gastroenterologists, endoscopists, and surgeons to guide and direct the taking of biopsies, specially in small cases, incipient or multiple stomach lesions.