Previous studies have shown that harvesting and plowing are the two most costly and labor intensive farm operations of grains. The combine conducts threshing and winnowing besides harvesting. Japanese combines are the widely spread and commonly- among other combines. Therefore, this study's objectives were to determine the most efficient Japanese combine for rice harvesting in Egypt. A set of technical and economic criteria as well as economic functions were estimated to evaluate the combine performances. Data used were the operating and financial records of the most common four combines for rice in Egypt in ace of the main agricultural engineering stations belonging to the ministry of agriculture. Results showed that whereas three combine types have not recognized the technical recommended operating rate, the "Kobotta 48 hp" achieved an operating rate of 115% The conduction rate ( number of hours to conduct one feddan) decreased along the useful life years of the combine . Within a certain brand the higher the combine power the less is the rate of conduction . It was 3.3 hrs for `Ynimar 33 hp", and 2.8 hrs for- 38 hp" while it was 1.93 hrs for "Kobotta 35 hp" and 1.66 hrs for -Kohere 48 hp". The brand "Kobotta" performed a higher relative profit margin per one pound of revenue than "Ynimar" brand . The most effective input in the variation of the profit per year is the served area followed by the costs of repair and horsepower, while the fuel and oil costs were insignificant. However, the first two effective variables are beyond the control of farm management . While the area served is a resultant of the demand for such service, the costs of repair and maintenance are to great extend a function of risk and uncertainty. Therefore the combine's power is the most decidable variable by the system operator. The higher the average costs (L.E./feddan. hp) the higher is the rate of conduction . Finally the quadratic estimated response faction showed that the optimum power in terms of horsepower that maximize the profit per combine per year is about 47 hp. All economic and technical criteria measured concluded that "Kobotta 48 hp" is the most efficient system for rice harvesting in Egypt. It is also concluded that the rental price of the combine should be associated with the operating hours rather than the served area.