The flow of cesium vapor from orifices and tubes into vacuum was investigated experimentally. Using a surface ionization gauge, the intensity of the flow field was measured at various angular positions from the center line for Knudsen numbers ranging from approximately 1 to 100. The dependence of the angular distribution and center-line intensity on Knudsen number is reported for cylindrical apertures having length-to-diameter ratios of 0.04, 1.15, 3.03, and 5.63.