Aim: Endoscopic color change of early gastric cancer was suggested to be correlated with mucosal vascularity. Using a hemoglobin index (IHb = 32 X log2 Vr/Vg) calculated from electronic endoscopic data, we investigated the mucosal hemoglobin volume and distribution of early gastric cancer. Methods: 47 intramucosal gastric carcinomas (29 differentiated carcinomas (DC) and 18 undifferentiated carcinomas (UC)) were studied. The IHb values of each of the picture elements of the linear region of interest (ROI), which was set on both cancerous and non-cancerous areas in the electronic endoscopic image, were determined. The mean IHb values of the cancerous lesion (IHb-C) and the non-cancerous mucosa (IHb-N) were calculated. The ratio of IHb-C to IHb-N was calculated and compared between the DC and UC groups. The pattern of distribution of mucosal hemoglobin was categorized, according to the wave form of the hemoglobin distribution curve on the linear ROI. Results: The median ratio of IHb-C and IHb-N in the DC was higher than that in the UC (1.21±0.082 (95 % confidence interval), 0.83±0.032, P < 0.001). The DC demonstrated three major patterns of hemoglobin distribution (i.e. mountainous, spicular and small wave-like patterns), while in the UC, the hemoglobin distribution curve showed a decreased or disappearing wave form, compared with that of non-cancerous mucosa. Conclusions: IHb could be one of the most useful markers to quantize the degree of color change in endoscopic images.