Spring emergence of the pink bollworm (PBW), Pectinophora gossypiella (Saunders) on Bt and non-Bt cotton was determined in the Comarca Lagunera, Mexico, during 1997 and 1998. There was no spring emergence of PBW or it was very low on Bt cotton during both years. These results indicate that spring emergence is drastically reduced in those areas where Bt cotton was planted the previous year, and explain largely the low infestation levels of PBW and the reduction of insecticide use in the Comarca Lagunera during the last two years.