In 1959, Bacillus thuringiensis Berliner (25×109 spores per Gram) at 2 and 4 pounds of wettable powder per acre was compared with: DDT, 1½ pounds; Sevin® (1-naphthyl N-methylearbamate), 2 pounds; heptachlor, 1.25 pounds; Dylox® (0,0-dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate) 2 pounds; and Kepone® (decachlorooetahydro-1,3,4-metheno-2H-cyclobuta [ed]pentalen-2-one), 1 pound. In 1960, two additional preparations, one (30×109 spores per gram) at 2 pounds per acre, the other (75×109 spores per gram) at 2 and 4 pounds, 2 pounds plus half dosage of DDT, and 2 pounds plus half dosage of Sevin were compared with DDT, Dylox and Kepone at the 1959 dosages, and Sevin at 1.2 pounds per acre for the control of the European corn borer, Ostrinia nubilalis (Hübner) on Sweet corn in southwestern Quebec. Each year, in early, July, two applications were made at a week interval with a commercial sprayer. Per cent infested plants and ears and numbers of borers in the plants and ears were obtained by dissecting at harvest 25 corn plants per replicate per treatment. In 1959, plots treated with DDT or Sevin gave more than 91% marketable ears; heptachlor, 84%; Kepone, Dylox, B. thuringiensis at 2 and 4 pounds, 72% to 77%. In 1960, DDT, Sevin, Dylox, Kepone, Thuricide (3O×109 spores per gram), B. thuringiensis at 4 pounds, and the bacillus plus DDT or Sevin gave more than 9.5% marketable ears; B. thuringiensis at 2 pounds, 88.5%. In 1959 only 58% of the cars in the untreated plots were marketable; in 1960,88%. The percentage of untreated plants damaged in 1959 Was 68; in 1960, 24. B. thuringiensis at 2 and 4 pounds per acre under heavy corn borer infestation was inferior to the standard DDT emulsion sprays and did not give adequate control. The results of this 2-year study indicate that susceptibility of the European corn borer to B. thuringiensis is rather low and inconsistent, and under heavy infestations, a relatively high dosage is required for satisfactory control.