Technical Abstract: Three greenhouse experiments were conducted in 2002 and 2003 to evaluate western corn rootworm, Diabrotica virgifera virgifera LeConte, adult emergence from transgenic corn that expresses the Cry3Bb1 endotoxin from the soil bacterium, Bacillus thuringiensis (Bt, MON 863), isoline corn, grassy weeds, and combinations thereof. One month after planting in 19 liter pots, 40 neonate western corn rootworm larvae were added. Weeds in the weeds + corn treatment involved giant foxtail, Setaria faberi R. A. W. Herrm, and large crabgrass Digitaria sanquinalis (L.) that were sprayed with glyphosate 5 d after adding larvae. In all three experiments, the number of beetles that emerged varied significantly. Generally, the total number of beetles recovered did not vary significantly between the isoline, isoline + weeds, and MON 863 + weeds, and more beetles were recovered from MON 863 + weeds than MON 863 alone or weeds alone. Beetle emergence from MON 863 + weeds was apparently enhanced by larvae that initially survived on weeds prior to application of glyphosate. Fecundity of females emerged from all treatments was also determined. The number of eggs laid per female was highest for females from the isoline corn and significantly fewer were laid from beetles reared MON 863 alone in trials for which data is available. Egg viability also varied significantly in parts of all three trials. Viability was generally lowest from those adults reared on MON 863, but viability was not always significantly lower for this treatment than for other treatments. The implications of these results in relation to insect resistant management are discussed.