Biological control of greenhouse whitefly, Trialeurodes vaporariorum in greenhouse tomatoes with the parasitoid Encarsia formosa has been evaluated in Korea. However implementation of biological control program is retarded due to the reasons that lacks of site specific strategies. Aims of the present research are: (1) To develop an effective biological control method of the whitefly in tomato plants; the following were studied: (a) development of proper introduction rate of parasitoid, E. formosa, for the control of whiteflies, and (b) development of the effective control method of American serpentine leafminers with a parasitoid, Diglyphus isaea. (2) To build a computer-simulation model in which all factors are incorporated which have been studied in the relationship between whitefly and the parasitoid. The computer-simulation models would be used to estimate the effect of future developments in the greenhouse industry on the biological control of the greenhouse whitefly using E. formosa. More general goals are to develop reliable evaluation techniques to test the pest-control ability of natural enemies prior to their use in practical situations and to determine which role simulation models may play in estimating the results of biological control in new situations.