Replicated field studies to evaluate the efficacy of transgenic cotton express-ing the delta endotoxin protein of Bacillus thuringiensis (B.t. cotton) against the cotton bollworm (Helicoverpa zea) (Boddie), the European corn borer (Ostrinia nubilalis) (Hubner) and stink bugs, primarily Acrosternum hilare (Say) and Euschistis servus (Say), were carried out in several representative cotton-producing areas in North Carolina from 1992 to 1995 under conditions of generally late planting (early to late May) and moderate to high bollworm pressure. In keeping with normal North Carolina cotton production practices, plots were neither irrigated nor treated with a disruptive overspray to enhance larval establishment. Overall, averaged over years and locations, the B.t. (BollgardTM) cotton lines evaluated (MON-81, MON 757 [BT-02], NuCOTN 33 and NuCOT35) expressed bollworm control and yields almost identical to the pyrethroid-protected, non-transformed varieties (Coker 312, DP-5415 and DP-5690) in both small plot and in larger-scale (2.5 to 5-acre) tests. European corn borer stem and boll damage were virtually non-existent in any of the studies. Stink bug damage to bolls in the B.t. lines, similar to the untransformed, unprotected lines, was at times significantly greater than that found in the pyrethroid- protected varieties (though typically, the damage was low to moderate), confirming that the Bollgard lines offered no protection against stink bugs, and also suggesting that stink bugs could become an economic consideration in some areas of North Carolina with the adoption of this technology. In comparing the Bollgard cotton lines with the untrans-formed, pyrethroid-protected lines for total boll damage (bollworm, European corn borer, fall armyworm and stink bug), averaged over all tests, years and locations (8 replicated comparisons), overall means were essentially the same.