Application of Bacillus thuringiensis Berliner and nuclear polyhedrosis virus (NPV) against gypsy moth, Lymantria dispar (L.), and Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), are reviewed. Applications of B. thuringiensis against gypsy moth started in 1960. Variations in dosage, application rate, number of applications, formulation, and types of spray nozzles were all tested. Single applications of 20 billion international units (BIU) of B. thuringiensis/ha applied with Beecomist^® nozzles gave sufficient foliage protection. Gypsy moth NPV has been applied at 2.5 × 10¹² polyhedra/ha in 2 different formulations. Both treatments gave foliage protection and reduced the larval population. Applications of 2.5 × 10¹¹ polyhedra/ha of Douglas-fir tussock moth NPV and 20 BIU/ha of B. thuringiensis in 25% molasses caused larval reductions of greater than 96% in 1973. In recent experiments, application rates, atomization, and formulations have all been varied.