In this paper are described the effects of the vane-angle β0 and the nozzle inclination-angle α0 and the annular slit ratio 2b0/D on the velocity and static pressure distributions in swirling and unswirled air jets issuing from annular nozzle. The following characteristics were clarified from the experiments : the characteristics of swirling jets (2b0/D<0.4) are mainly affected by β0 and slightly by α0 and 2b0/D. In the case of β0<60°, a region of subatmospheric pressure exists near the nozzle exit. Therefore, main stream lines of the jet are deflected toward the nozzle axis, and the main stream surface formed by these lines becomes asymptotically a cylindrical surface in far downstream region. The unswirled annular jets become circular ones at a short distance from the nozzle exit. The characteristics of the jet in the downstream region are similar to those of circular free jet.