The paper discusses the mechanics for decomposing the total change in per hectare rice output owitig to inception of new production technology among various components, as well as to ascertain the technical bias of the new rice production technology with respect to different factor inputs especially in the north and south regions of Bihar. The analysis reveals that the contribution of new rice production technology is more pronounced in southern region as compared to the northern region of the state. With the introduction of high yielding varieties of rice, per hectare production was found to be 43.47 per cent and 47.77 per cent higher in northern and southern regions, resp.ectively. Moreover, the technological bias with respect to factor inputs in rice production was estimated as land and labour saving as well as fertilizer, and capital using in northern region, though it was found to be statistically non-significant. In southern region of the state, technological bias was observed as labour, fertilizer and capital using on one hand and land-saving on the other. However, the technical bias was found to be statistically significant only in case of capital and land.