This study intended to develop the prediction models of the traction and field performance of two-wheel tractors by using the principles which were applied for predicting those of the four-wheel tractors. The traction model developed in this study consists of the net traction coefficient, rolling resistance coefficient and traction efficiency, Which are expressed as functions of both wheel numeric and slip. A computer program on the field performance of two-wheel tractors is also developed to predict the drawbar horsepower, traction force, traction efficiency, rotational speed of engine and engine horsepower if the characteristics of the engine performance and operational condition of the two-wheel tractor are known. Based on the developed models, the conditions of basic variables to maximize the field performance were analyzed so as to assess the existing two-wheel tractor.