Laboratory, semi field and field tests to assess the side effects of 20 pesticides on 19 different beneficial organisms were carried out by members of the Working Group “Pesticides and Beneficial Organisms” of the International Organization for Biological Control (IOBC), West Palearctic Regional Section (WPRS). This 5th joint pesticide testing programme of the working group was carried out by 21 participants in 11 European countries. The pesticides (7 insecticides, 8 fungicides and 5 herbicides), that were chosen for their possible selectivity, were tested according to internationally approved principles.