An expert system for cotton pest management, rbWHIMS, has been under development for 3.5 years as part of the USDA, ARS GOSSYM/COMAX Project. This computer-based system was evaluated in the field for the first time in 1991. Tests were conducted on three farms in Mississippi, and at several locations in Missouri and Tennessee. WHIMS made pest management recommendations for nine groups of arthropod species on about 800 acres of cotton. Federal and state personnel took part in the work. This paper describes the objectives of the Mississippi research, and a critical evaluation of the performance of the user interface, rule base, and WHIMS report. Results are being used to improve the functionality and ease-of-operation of WHIMS for 1992.