This paper is concerned with the statistical analyses of model test results in still water of high speed craft from the practical view-point to design crafts from 10 to 100 tons operating in Japanese waters. Test results are analysed by statistical regression methods, after carrying out towing tests of 78 models. Among many mathematical models of regression equations which will be considered within 3.5 of Froude number F _∇= V /√∇^1/3 g , three models including (1) algebraic sum of eleven hull form parameters, (2) addition of L ², θ L and θ² terms to (1), and (3) the model which designers will desire, are chosen and discussed. The range of application of these regression equations is assumed such as a n -dimensional tolerance elliptic quadric. The influence of each hull form parameter on hydrodynamic characteristics in still water is discussed by obtaining the correlation coefficients between test results and hull form parameters. As an example the effective horse power of an actual ship is numerically calculated by using obtained regression equations.