A theoretical study has been conducted to determine the effects of rotation, inflow, and forward flight on the development of the laminar boundary layer on a helicopter blade. Particular emphasis was placed on the determination of the separation line. In order to faciliate the computation of the inviscid flow about the blade, an 11.9-thick symmetrical Joukowski airfoil was used. The essential feature of the analysis was the scaling of the chordwise coordinate so that the separation line is invariant with span and time in the transformed coordinate system. The transformed boundary layer equations were expanded in an asymptotic series in span, and the resulting equations were solved. The major effect of rotation is noted as a delay in separation.