The results of comparative study on Nd: YAG laser therapy (YAG) and photodynamic therapy using hematoporphyrin and argon dye laser (PDT) were reported.The lesions were 60 endoscopically diagnosed early gastric cancers which were treated by either YAG (30 lesions) or PDT (30 lesions) more than 5 years ago Complete response (CR), disappearance of all tumor with negative biopsy for cancer which persisted for at least 4 weeks, were obtained in 16 of 30 (53%) lesions treated by YAG and 22 of 30 (73%) lesions treated by PDT. Recurrence of tumor was observed in 19% of the cases of YAG and 41% of the cases of PDT. For the lesions less than 1 cm, CR rates of YAG and PDT were 92%, 100%, and recurrence rates were 9%, 0%, respectively. For the lesions less than 2 cm,CR rates of YAG and PDT were 56%, 82% and recurrence rates were 7%, 44%, respectively. The efficacy (negative biopsy for cancer after the initial therapy) of YAG and PDT for the lesions less than 2 cm were 52% and 15%.For the lesions exceeded 2 cm,CR was obtained in 2 of 5 (40%) of the lesions treated by YAG, but all the 2 lesions recurred after the initial therapy. CR rate of PDT was 50%(4 of 6 lesions) with recurrence rate of 25%.Therefore, there were no significant differences in the efficacy of the initial therapy of YAG and PDT, if the size of lesion was less than 2 cm. However, PDT was superior to YAG if the lesion exceeded 2 cm.