The western flower thrip Frankliniella occidentalis (Pergande) (WFT) and the two-spotted spider mite Tetranychus urticae Koch (TSSM) are notorious pests of ornamentals and vegetables in greenhouses.Plants are often simultaneously infested by both pests.The predatory mite Amblyseius cucumeris (Oudemans)has been widely used as a biological control agent for thrips in greenhouses and has sometimes also been used to control TSSM.We here report the results of investigations on the biological control of WFT and TSSM by A.cucumeris on kidney beans in pot trails.At low and moderate, but not high, TSSM densities, A.cucumeris released at a predator:prey ratio of 1:4 significantly suppressed TSSM populations.5 and 10 A.cucumeris could also significantly suppress 20 and 40 WFT after 8 days.The control efficiency of WFT by A.cucumeris was not significantly affected by the presence of TSSM.WFT larvae can successfully prey on the eggs of A.cucumeris, consuming an average number of 1.2 eggs per day.The potential for the biological control of WFT in greenhouses by A.cucumeris is discussed.