The seeds of a number of Brassica L. species are cultivated for the production of oil. Collectively, the oilseed Brassica sp., generally referred to as rapeseed, supply more than 13% of the world's supply of edible oils and rank third behind soybean and oil palm in importance. The term "canola" was adopted by the Canadians in 1979 and used to describe oilseed Brassica cultivars that produce oils containing less than 2% erucic acid and to describe defatted seed meals with less than 30 pmol g-' of aliphatic glucosinolates. Brassica napus L. canola cultivars are currently dominant in U.S. production, although canola-quality Brassica rapa (synonymous with Brassica campestris) cultivars also exist (Raymer et al., 1990).Production of canola in the U.S. has grown at a modest rate during the last 10 years from virtually O in 1985 to 165,000 ha in 1995 (C. Boynton, U.S. Canola Association, personal communication). As production of canola continues to grow, insect problems are expected to become more serious (Lamb, 1989). This may be particularly true as canola production expands in the southeastern United States and California, where mild winter temperatures are likely to lead to increased herbivory, as compared with the much cooler areas (e.g. Canada), where canola has historically been produced. Ubiquitous lepidopteran Brassica specialists, such as the DBM and the CBL, and generalist lepidop-terans, such as the BAW and CEW, may increase in importance where canola is grown in warmer regions (Buntin and Raymer, 1994). This scenario may be especially viable with regard to generalist herbivores, since glucosinolates, a hypothesized antiherbivorant to generalist insects (Giamoustaris and Mithen, 1995), have been bred out of canola-quality rapeseed. Transgenic canola cultivars with insecticidal properties will certainly play a major role in integrated pest management strategies for canola pests (Talekar and Shelton, 1993;Evans and Scarisbrick, 1994). The objectives for this study were 2-fold. (a) To determine the effect of Bt expression in B. napus on antibiosis for severa1 lepidopteran insects. Unlike the related Bt soybean study (Stewart et al., 1996), in which only few, low-expressing synthetic Bacillus thuringiensis insecticidal crystal protein ( B t crylAc) plants were produced, the likelihood of obtaining a wide range of B t expression is greater using a species that is more amenable to genetic transformation, such as B. napus. (b) To develop biological tools to test models pertaining to biotechnological risk assessment. It is possible that a plant species, such as B. napus, that is able to persist in nonagricultural environments could become more weedy in a transgenic form if the transgene confers an increment of fitness and the plant is naturalized in areas of its cultivation. Thus, we developed the B t canola to ultimately test population-leve1 ecological hypotheses.