The nuclear-polyhedrosis virus of the cabbage looper, Trichoplusia ni (Hübner), the granulosis virus of the imported cabbage worm, Pieris rapae (L.), formulations or Bacillus thuringiensis Berliner, and chemical insecticides were compared for control of T. ni and P. rapae larvae on cabbage in plot tests in southern Ontario in 1969 and 1970. In 1970, 4 applications of mixtures of the viruses (6×1012T. ni polyhedra and 1 × 1013P. rapae granules/ha) controlled the respective hosts as well as did 4 applications of endosulfan (0.84 kg/ha) or of Thuricide 90TS® (5.6 l/ha), a formulation of B. thuringiensis. Experimental formulations of B. thuringiensis (Thuricide HP® and Dipel HD-l®) were more effective than the Thuricide 90TS formulation. Tests in large plots in growers fields also demonstrated efficacy of the viruses. The combination of viruses with chemical insecticides in the spray program was especially effective.