In the paper have been present results of fatigue-shear strength investigations of fitted screws M16x1, in accordance with the standard PN-91/M-82342. One applied one-sided periodical tension at five levels of shearing stress of 15 fitted screws in double shearing samples. On the base of investigation results, with the least squares method one worked out an equalization of regression line. One calculated a factor of lineal correlation and stated a confidence region. From the equalization of regression line for 2*106 cycles of load one calculated save fatigue life Ztj = 215 MPa.