Since 1983 several improvements in the sexually sterile boll weevil program have been developed that should impact on the efficiency of mass rearing and its successful field release. The mass-released sterile weevil competitiveness was raised from that of ca. 6% found for the weevils released in the Boll Weevil Eradication Trial of 1979 to more than 25% and the LT(50) increased by more than 1.5 days by the use of 0.03% chloramphenicol, kanamycin and penicillin V in the pre-irradiated adult diet. Combinations of loose sandy soil and ground temperatures above 46 C (common occurrence in cotton fields) which were found to be detrimental to air dropped free fall weevils should be alleviated by a containerized release. An alternative ground release procedure has been developed and tested which applies weevils directly to the cotton plant thus avoiding adverse field conditions. Finally, a method of stockpiling the mass-reared weevils for six weeks has been developed by lowering the temperature from 31 to 20 C from the egg stage through pupation. These developments overcome past difficulties to an extent that suggests a sterile release program should receive further large-scale field testing.