How market factors affected the diffusion of four agricultural inputs (fertilizer, herbicide, insecticide, and fungicide) among farmers on the Central Plain of Thailand is examined. Market factors investigated were the distribution policies of the propagators and the travel behavior of the potential adopters. Data were gathered through personal interviews with farmers, agents of the Ministry of Agriculture, extension agents, companies, and merchants. The analysis of the spatial diffusion of the four agricultural inputs revealed that the two market factors not only played a major role in shaping their diffusion but the patterns that evolved differed from previous research based on the information flow perspective. Not all prospective adopters had the same opportunity to adopt. For example, information concerning innovations which emanated from the Ministry of Agriculture enabled provinces and counties, which they perceived to be in greater need, to receive the information first. At the local level, the promotional activities of the extension agents excluded private entrepreneurs in the urban centers and were limited to those villages where the agent perceived there to be the greatest potential for success. Many farmers willingly traveled as much as 50 kilometers to acquire information. Inputs, therefore, often diffused to the village level before they were available in the lowest order urban centers. Access of farmers to information through informing was rare. Farmers gained information about inputs primarily through seeking from fellow farmers and sources in urban centers. (RM)