Successful cultivation of cigarette tobacco has not been possible in the Hyderabad and Khairpur Divisions due to Leaf Curl'. Studies were conducted in 1959-60 to investigate extent of influence of environmental temperature on severity of 'Leaf Curl' on variety 'Harrisons Special' of cigarette tobacco. 15th August and 30th August transplanting dates were compared with 15th October, 30th October and 15th November. weekly increase in percentage severity of 'Leaf Curl' correlated with the respective weekly mean temperatures. Average simple correlation coefficient was found to be positive and highly significant (0.6445) .As the transplanting time was advanced the total infection declined. Least infection was obtained in the 15th November transplanting.