Changes in production variability and their sources were measured for six crops - Aus rice, Aman rice, Boro rice, jute, wheat, and sugarcane between two time periods - pre-modern technology adoption period (1947/48 - 1967/68) and modern technology (MT) adoption period (1968/69 - 1986/87). For wheat, these periods were 1947/48 - 1971/72 and 1972/73 - 1986/87 respectively. The results showed that in MT period (i) both the absolute and relative variability decreased in case of Aus, Aman and sugarcane; (ii) both the absolute and relative variability increased in case of jute; and (iii) absolute variability increased but relative variability decreased in case of Boro rice and wheat. The decrease in coefficient of variation (CV) of Aus, Aman and sugarcane production is due to decrease in variance and increase in production . The decrease in CV of Boro rice and wheat production is attributed to an increase in average production of Boro rice and wheat. But the increase in production variance is not attributed to MT. The increase in relative variability of jute is due to increase in absolute variability and decrease in average production of jute during MT period.