Evaluation of Commercial Silkworm Varieties and Rearing Practices in Villages of North-Eastern Thailand. A silkworm evaluation programme of poly-into-bivoltine and bivoltine hybrid varieties has been undertaken during one year in traditional sericultural villages of north-eastern Thailand. Data were collected in a way that climatic constraints and technical problems encountered by rearers could also be identified. The results analysis shows that it is necessary to choose adequate silkworm varieties and to adapt rearing practices according to the season and the overall technical level of sericultural management in the village. In the dry season, practically ail varieties have similar performances. However, special measures related to young silkworm rearing are crucial to ensure a satisfactory yield. On the contrary, in the wet season some varieties are more affected than others by silkworm diseases. When the technical level of sericulture management is low, it is recommended tu use a variety showing a reliable yield. In order to compensate unfavourable rearing conditions and consequently reduce the incidence of silkworm diseases, it is advocated to modify some traditional rearing practices.