Development of adventitious roots in tobacco grown on pots and fields was investigated as follows: 1) Adventitious roots of tobacco appeared on stem about 20 days after soil dressing and spread conspicuously during the stage from budding to flowering. 2) Comparisons among 3 varieties differing in budding time revealed that development of adventitious roots had a close connection with the time of budding, namely, the development was the earliest in the early budding type of tobacco and the latest in the late one. 3) Topping accerelated the development of adventitious roots. 4) From the facts mentioned above, it seems to be very important for cultivation practice to promote the growth of tap roots and to accelate early growth of tobacco to hasten the development of adventitious roots.