For many years, we have been conducting studies to develop a general theory of diffusion process from view point of communication sciences. The present research is a part of a series of researches directed toward developing a general theory. The primary aims of this research are : 1) to test the applicability of various hypotheses pertaing to the diffusion of innovation, which have been developed by scholars abroad, to the case of diffusion of small-size farm tractors within a small rural community in Japan. 2) to discuss the various conditional factors leading to the applicability or non-applicability of these hypotheses to the rural community in question. Small-size tractors started appearing in Japan around 1955 and around 1960 began to gain increasing popularity at a very fast rate. By the year 1968, over three million of these tractors have been in active use throughout Japan. Due to this wide spread acceptance of small-size tractors, plowing operations, which formerly had been relying on heavy labour utilizing both human and animal power, have been conducted with the assist of mechanical power. In relation to this wide-spread acceptance by the year 1967, 95.8% of paddy (rice) field and 60.3% of field have beeen plowed with mechanical power, whereas the respective figures for the year 1960 were 25.5% and 11.8%. It can be noted that there were in general four major factors conducive to the wide acceptance of small-size tractors within Japan. 1) Shortage of agricultural labor due to the sizeable flow of agricultural population to the secondary and tertiary industries. 2) Necessity to simplify agricultural operations to permit higher income from side business aside from agriculture within agricultural households. 3) Desire to reduce the burden of heavy labor. 4) Financial assistance from both the national and local governments to assist the purchase of small size tractors. The field study for this research was conducted in Hachioji village (population 168 households) within Oguni town in Niigata Prefecture. Small size tractors began appearing in Hachioji around 1957 and by 1967 88% of all agricultural household in the village has acquired these tractors. The following hypotheses of diffusion process were tested in this Hachioji Study. Hypothesis 1. Mass media information sources are most important at awareness stage and Self information sources are most important at adoption stage. Hypothesis 2-1. Mass media information sources are most important , at awareness stage, 2-2. and personal information sources are most important at adoption stage. Hypothesis 3-1. Cosmopolite information sources are most important at awareness stage, 3-2. and localite information sources are most important at adoption stage. Hypothesis 4. Mass media information sources are more important at awareness stage than at adoption stage. Hypothesis 5. Agricultural Agencies information sources are more important at adoption stage than at awareness stage. Hypothesis 6. Impersonal sources of information are more important than personal sources for relatively earlier adopters of innovation than for later adopters. Hypothesis 7. Cosmopolite sources of information are more important than localite sources for relatively earlier adopters of innovation than later adopters. Hypothesis 8. Adopter distributions follow a bell-shaped curve over time and approach normality. Hypothesis 9. Awareness proceeds at a more rapid rate than does adoption. Hypothesis 10. Pairs of sociometricly related individuals adopt the innovation at about same time. of the above hypotheses, H2-2, H3-1, H4, H5, H7, H8, and H10 were applicable to the diffusion process of the Small Size Tractors in Hachioji village. H1, H2-1, H3-2, H6, and H9 were not applicable.