This article attempts to clarify the general characters, structures and social significance of the subsidiary works carried on by the farmers in the principal sericultural regions of Japan, by examining their various patterns and percentages and investigating their major regional types. General conclusions reached are as follows. Farmers in the highland areas are on the whole inclined to stick to sericulture associated with some side jobs carried on rather spontaneously for the purpose of obtaining cash or making use of their spare time. The extension and intensification of their side jobs, which have traditionally formed the essential part of their farming, can be found among almost all classes of farmers, instead of being limited to particular size categories. Consequently this tendency is not necessarily connected with the disintegration of farming population, the complete abondonment of agriculture, nor desertion of rural villages. In the flat areas, on the other hand, the conspicuous development of industries has been turning over an increasing number of farmers into a sort of town workers, making their farming less intensive and causing a remarkable decrease in sericultural farmers. Such multiplication of farmers engaged simultaneously in other ocupations as a result of urbanization and industrialization of local communities, is driving many of the small farmers away from their farms and at the same time bringing forth some intensified and diversified farming led by full-time farmers as in sericulture, horticulture and diary, so that the polarization and disintegration of farmers are noticeably stimulated. Generally speaking, in recent years more sericultural farmers in Japan have been increasingly engaged in subsidiary jobs, while full-time farmers engaged solely in agriculture have greatly decreased. This tendency, which seems to be accelerated in future, is closely related with the gradual increase in the relative importance of the highland areas for sericultural production, where spontaneous side works are more popular among the highland farmers than in the flat areas.