Annually, large tracts of forest in eastern Canada are sprayed aerially with insecticides (fenitrothion, aminocarb) in attempts to control an epidemic infestation by an indigenous forest pest, the spruce budworm (Choristoneura fumiferana, Clemens). The massive size of the spraying programs, the anecdotal reports of human exposure, and the potential for hazard to human health have led one province. New Brunswick, to initiate and fund specific environmental and laboratory studies which will provide adequate data upon which the government can base realistic legislation to protect both the forests and the population. These studies have included some unique field analyses of aerial spray drift conducted by a research group from the National Research Council; comparative subchronic studies in rats of fenitrothion and a new formulation; a nose-only inhalation study of this formulation in rats; field testing of the formulation for drift characteristics. Ongoing research involves the subchronic testing of the emulsifying agents being used routinely in the new formulation and studies of a low-drift additive which will stabilize the particle size of the spray. On the basis of the results to date, the government has been able to modify spraying techniques and to establish realistic buffer zones around human habitation.