The performance of Bollgard and non-Bollgard (conventional) varieties, based on lint yields/acre, were examined in 9 and 8 county variety trials in 1998 and 1999 respectively. These were planted and managed as on-farm, large plots for weed and insect control. Bollgard varieties produced an 85 lb and 17 lb lint yield/acre increase averaged across all locations in 1998 and 1999, respectively. Yield differences for Bollgard vs non-Bollgard at individual field sites ranged from -29 lbs to +339 lbs in 1998 and -77 lbs to +132 lbs in 1999. Average insect control cost per acre for Bollgard was $65 and $62 versus non-Bollgard at $62 and $46 for 1998 and 1999, respectively. Bollgard varieties performed equal to or better than non-Bollgard varieties in the presence of higher bollworm, tobacco budworm, and European corn borer infestations. In the absence of these insects or when insecticide treatments were effective, conventional varieties performed equal to or better than Bollgard varieties. There were numerical lint yield/acre differences among varieties within a location and among locations in both 1998 and 1999.