Abstract The paper presents the analysis and the results of the jet pump applications in the two biggest Italian heavy oil fields: Vega (15 °API) in offshore Sicily and Gela (9 °API) in onshore Sicily. In both fields the water cut is as much as 50% and most of the wells produce in artifiCial lifting: ESP, diluent lift and rod pumps are the three methods used. The tests with jet pumps were motivated by the need to use a cheaper artificial lifting method. The objective was, in fact, to reduce both the workover costs for replacing the failed pumps and the operating costs of the wells producing in diluent lifting. Various jet pumps sizes, types and rate of the power fluids were experienced. Accurate measurements of the pressure above and below the jet pumps were recorded allowing comparison of the field performance with the theoretical one. The field test campaign finished in 1991/1992 and demonstrated that the jet pump, despite its low efficiency ( 30 - 60 % lower than expected ) and flexibility, is an efficient and cost-effective way to produce heavy oils. The jet pump installation costs, in four wells, have been 6-9 times less than workover costs for replacing ESP. We deem that the conclusions of the study can be useful also in the application of jet pumping in other heavy oil fields.