The trials conducted with selected chemical and biological insecticides in 1998-2000 showed the highest effectiveness of Karate Zeon 100 CS (lambda-cyhalotrine) in European corn borer (ECB) larvae control in sweet corn. The efficacy of biological insecticides containing Bacillus thuringiensis ssp. kurstaki: Biobit 3.2 WP and Lepinox WDG was very variable between the years. Reasons for insufficient efficacy of these products are discussed. The most appropriate time for the application of a chemical insecticide against ECB larvae are plant developmental stages since the beginning of pollen shedding to full blooming (63–67 BBCH scale). The efficacy of treatment was the highest at that time.