When the edentulous posterior maxilla shows severe atrophy (Cawood and Howell Class V to VI), the traditional approach requires at least two surgical procedures. The first is a sinus lift (alone or with guided bone regeneration), and the second is to position implants. This article illustrates a technique that allows threedimensional reconstruction of the sinus, placing an allogenous fresh bone block and simultaneous implant positioning using a computer-guided implant surgery.