The susceptibility of first instars and adults of Chrysopa oculata Say to pesticides used in tree fruit production in Ontario was assessed. Most organophosphorous insecticides except phosalone were toxic to both stages. The synthetic pyrethroids, with the exception of fenvalerate and flucythrinate, were generally more toxic than organophosphorous insecticides. Adults and first instars were equally susceptible to most insecticides. The acaricides and fungicides were not toxic at the levels tested. Methomyl and carbaryl were toxic to both stages, but pirimicarb was almost nontoxic. DDT and endosulfan were toxic only at high concentrations. Reasons for differences in toxicities were not investigated. In the field, azinphosmethyl and phosmet were toxic to larvae for at least 14 days. Permethrin killed larvae caged on foliage for ca. 10 days, whereas most survived on phosalone-treated foliage 1 day after application.