A double achromatic magnet system is described which bends electrons of moderate to high clinical energy (2 MeV to 30 MeV) through 112.5° onto a target. The X-ray or electron beam emerging from the target is used for medical therapy. By providing quadrupole and sextupole corrections to the bending magnets, a spot size of 2 × 2 mm 2 at the target is obtained as well as double achromatic behaviour, for electron beams with a large relative energy spread of 10%, an initial width and height of 5 mm, and with an initial divergence spread of ± 1 mrad. The corrections have been introduced on the basis of field measurements in the median plane of the bending system, and subsequent trajectory calculations. The effects agree with numerical results obtained by running a second-order particle transport code on the predicted magnet shape.