A new roentgenographic unit for skull roentgenography, pneumoencephalography, ventriculography, and angiography is described. The unit incorporates a chair which will somersault the patient completely in a forward or backward direction, keeping the center of the head at a fixed point in space. The frontal projections are obtained with the central ray passing from [See Figure in the PDF file] behind forward, and with the film always at 90° to the central ray, giving a minimum of distortion. Midline tomography (autotomography) is performed mechanically, and linear laminagraphy may also be performed with the patient in any position.