The impact problem for a rigid-plastic beam is formulated by using an interaction curve relating shearing force and bending moment for fully plastic action, and allowing for shear and rotary inertia effects. Using a simplified interaction diagram, the problem of point-impact loading is solved for a special case. The analysis shows that the shear effects are of considerable importance when the parameter µ0 = 2Q0l/M0 is less than 20 where Qo and Mo are plastic-carrying capacities of the cross section for pure shear and bending, respectively, and 21 is the length of the beam. © 1960 by ASME.