Abstract Ecopetrol and OXY signed in september 2005 a commercial and technical agreement to increase the oil and gas production in La Cira - Infantas, a mature oilfield located in the Magdalena Middle Valley basin in Colombia, which was discovered in 1918. The East and North areas of La Cira - Infantas field had in 2006, 107 producers and 21 injectors active wells and has been waterflooded since 1957. This paper illustrate the methodology used and the results obtained in the estimation of the areal and vertical efficiencies of the waterflooding process using the analytical method of Craig, Geffen and Morsen applied by the use of a software developed by Ecopetrol S.A called ASIA (Advanced System for Injection Analysis). Available information analysis, databases generation, pattern definition, and history matching were the main considerations applied to implement the methodology which let us to identify non irrupted sands, non swept zones, water losses, existing pattern real status and real performance of the waterflood process in the selected area. Analytical simulation results showed that the system had serious problems related to lack of hydraulic connectivity between producers and injectors sands and water that had been pumped out of interest zones which were related to zones near to a faulty area. Calculations obtained using the ASIA software, showed that only 233 millions of barrels had been effectively injected in the area, it does mean that nearly 38% of the injected water had been lost. After this evaluation, Ecopetrol and OXY began an aggressive program of activation of producing wells and injectors and configuring new patterns of injection, a strategy that has led to increase the production of the area in about 3000 bopd. The application of this methodology using the ASIA software will help in designing and surveillance of waterflooding process in other Colombia fields. Prior knowledge of waterflooding conditions will help in defining better strategies and conditions for the process.