Six insecticides (Malathion, Quik, Cidial, Dimethoate, Actellic, Deltamethrin) and two mineral oils (Super misrona and Kemesol) are currently used to control the most important pests in Mediterranean olive cultivation (olive fly, olive moth and black scale). Potential side-effects of these compounds were tested on the egg parasitoid Trichogramma cacoeciae Marchal, following recommendations of the working group ÔPesticides and Beneficial OrganismsÕ of the International Organization for Biological Control, West Palaearctic Regional Section (IOBC/ WPRS). In the present study, three different types of test methods were carried out: (1) initial toxicity dose-response test on adult wasps; (2) initial toxicity test on pupae, using field recommended rates; and (3) persistent test on olive foliage to assess the duration of harmful activity. The six insecticides tested reduced parasitism by 80-95% and rated as moderately harmful at the field recommended doses. The two mineral oils reduced parasitism up to 25% and were therefore rated as harmless to the adult stage of the parasitoid. The results of the pupal test (parasitoid pupa inside the host egg) showed that Malathion was harmless; Quik, Actellic and Cidial were slightly harmful, while Dimethoate and Deltamethrin were moderately harmful. The results of the persistence test on olive foliage showed that Malathion, Quik and Actellic were slightly persistent, while Cidial, Dimethoate and Deltamethrin were moderately persistent.