A study has been made of the effects of free stream oscillations on laminar boundary layers of the Howarth type. Detailed measurements of oscillations have been made for the two conditions of Blasius flow and a Howarth flow fairly near separation. It has been found that there are three types of behavior, corresponding to low, intermediate, and high frequencies. Low and very high frequency oscillations are shown to be well described by existing approximate solutions. However, an intermediate frequency region required a new analytic treatment, the results of which do in fact account for the measured flow behavior in that region.