Uniform radiologic exposure from the pelvis to the ankles is often difficult to achieve when long films (51-inch) are used for femoral angiography. A unique device developed to shape the x-ray beam accomplishes this task by using a movable shutter to obscure a portion of the x-ray beam. A microprocessor-controlled stepper motor modulates the amount of beam cutoff by regulating the movement of the shutter from the foot end of the film. The goal is to match exposure factors to the patient's body shape. This beam-shaping device has been evaluated and tested in examinations of 500 patients over the past year. A substantial improvement in image quality over that achieved with earlier systems of graduated screens and multiple wedge filters was seen in all cases. The system is esy to use, flexible, and especially valuable in imaging obese patients or those who have legs disproportionately smaller than their pelvis or abdomen.