An analysis of the diffusion process of information or of pervading fashionable custom may make it possible to infer the regional system as a diffusion channel. From this viewpoint the writer attempted to explain how a regional system had operated in the Okagemairi diffusion in the year of 1771. Though the custom of visiting the Ise Shrines once in one's life had been widespread among the Japanese during the Fdo era (1603-1867), under the feudal system, it was impossible for wives and children, or employees to visit without participating in the Okagemairi, a phenomenon of group pilgrimage. A custom of Okagemairi usually began with rumors about the falling of charms of the Ise Shrines from heavens as a start, and people along the route offered food and money or free lodging to vistiors. As visitors consequently could travel without money, many people participated in the Okage-mairi within a short period.<br> From Mr. Kosen Mori's diary, who lived at Matsuzaka in Ise province, we come to know the date when the first participants from each province passed through Matsuzaka, as shown in the 4th column of Table I. The writer determined the date when participants started from province, as shown in the 5th column o Table 1, assuming that they walked 30km. per day along the shortest path shown in Fig. 2. He assumed this date as that of the diffusion, or as the date when the Okagemairi spread to each province.<br> Trend surface analysis of the date of diffusion revealed the following points (Fig. 5) (1) The fact that the explained variance of quadratic trend surface is 39.26% suggest: that the Okagemairi contagiously spread from Yamashiro, the starting point of diffusion. (2) The fact that the diffusion to Musashi and Settsu was much earlier than the general trend, and the fact that the diffusion to Tajima, Inaba, Mimasaka and Hoki was much later than the general trend, suggest that the population size effect was partially in operation (Fig. 6).<br> (3) As there is almost no correlation between residual and population size (γ-0.1959), the determinant to warp the ellipse-like diffusion pattern seems to be a short-circuit effect through sea routes rather than the population size effect. This point is suggested by the fact that the diffusion to Nagato and its surrounding provinces, where the westward Liner linking the Hokuriku region with Osaka via the Inland Sea of Seto, the Setouchi Liner and the Kyushu Liner stopped, was much earlier than the general trend, and also by the fact that the diffusion to Ecchu and Echigo in the Hokuriku region, which had been connected with Osaka and Kyoto by ship before the Edo era, was much earlier than the general trend.<br> (4) The fact that the Okagemairi did not spread to Noto, Hida, Kai, Kazusa and Awa (_??_), and the fact that the diffusion to Suruga was much later than the general trend, suggest that believers in the Jodoshinshu sect and the Nichirenshu sect in these provinces resisted the Ise faith (Fig. 4).<br> (5) The fact that most of the provinces mentioned in (4) are also located in mountainous or peninsular areas, and the fact that the diffusion to Shinano which is surrounded by the Chubu Mountains was much later than the general trend, suggest that physical and site factors delayed the Okagemairi diffusion.<br> Finally, in order to examine the above points from the aspect of spatial process, the writer simulated the information diffusion from Yamashiro by the gravity-type Monte Carlo simulation model whose flow-diagram and program are shown in Fig. 7 and in Appendix respectively. Fig. 8 shows the average output of 50 simulation runs of Model I whose coefficient of distance friction was determined to be 3.0 by the iterative method.