the oregano is a plant, rich in essential oil and very used as spice in the preparation of foods. the objective of this paper was to analyze the viability of irrigation for oregano in presidente prudente, s？o paulo state, brazil, including economic risk factors, their effect on irrigation total cost, as well as the different pumping kinds. the monte carlo simulation was utilized to study the economic factors: fixed cost, labor, maintenance, pumping and water. the use of irrigation for the oregano in the region of presidente prudente is indicated because of its economic feasibility and the reduced risks. the average values of the benefit/cost for all water depths tested were higher than 1, indicating viability. the use of irrigation promoted lower risks compared to the non irrigated crop. the micro irrigation system presented greater sensitivity to changes of prices of the equipment associated to the variation of the useful life of the system. the oregano selling price was the most important factor involved in annual net profit. the water cost was the factor of lesser influence on the total cost. due to the characteristic of high drip irrigation frequency there was no difference between the tariffs based in use hour of electric energy classified as green and blue, which are characterized by applying different rates on the energy consumption and demand according to the hours of day and times of the year. for the studied region it was recommended drip irrigation water management of oregano with the daily application of 100% of pan evaporation class a using electric motor with tariffs blue or green.