The flow field characteristics of an axisymmetric pulsed jet at operating conditions of Mj = 0.3, 0.65 and 0.8 are described using phase locked Particle Image Velocimetry (PIV) measurements. The pulsation in the jet flow is obtained by a rotating disk. Unlike piston generated incompressible pulse flows or shock wave generated supersonic pulse flows, a sinusoidal pulsation is added on a small amount of leaking base flow. The formation of vortex rings and the associated velocity, vorticity and entrainment fields are investigated changing pulsation frequency. In addition to the description of the flow properties by means of PIV, unsteady pressure measurements, near field acoustic measurements and thrust measurements are also made to explain the flow dynamics involved in pulsed jets. The results show that the initial region of the flow is dominated by the periodic turbulent stresses where a major increase in the mass flux and the entrainment has been measured. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.