Part of the boll weevil, Anthonomus grandis Boh., population enters diapause during late summer and early fall in Louisiana. Winter is passed in this condition. Diapause in this insect is characterized by cessation of gametogenesis and atrophy of gonads, increase in fat content, decrease in water content, and decrease in respiratory rate. Diapausing boll weevils were found in ground trash each month of the year except June and July. It is almost certain that they were also present there during these 2 months but no collections of ground trash were made at this time. Diapause occurred in some individuals as early as July 30 and movement to winter quarters began prior to August 16 during 1957. Fat and water content remained relatively stable in diapausing weevils during late fall, winter and early spring. There was a sharp decrease in fat and a corresponding increase in water content soon after they moved back to cotton in the spring. Males were able to resume spermatogenesis prior to leaving their winter quarters but oogenesis did not begin until the females had fed on seedling cotton.