A selective aperture for a laser delivery system for providing incision, ablation and coagulation. A laser crystal disposed between two reflective surfaces forms a laser beam. An aperture member positioned between the laser crystal and one of the reflective surfaces includes a substantially circular aperture for passing the laser beam. The size of the aperture is selectively adjustable. The aperture member has a plurality of apertures of various different sizes and is rotatable about an axis of rotation. The axis of rotation is parallel to the longitudinal axis of the laser crystal. By appropriately rotating the aperture member, a selected one of the apertures is positioned to pass the laser beam. A stepper motor and flexible shaft are utilized for rotating the aperture member. At least one of the apertures is surrounded by a beveled portion of the rotatable member. Alternatively, two lasers with different size fixed apertures could be utilized and directed to a common surface. According to an aspect of the invention, an articulated arm is provided along with one or more refocussing optics for refocussing the laser beam as it travels through the arm. According to another aspect, a second laser source is provided along with a galvanometer for directing each of two laser beams to a surface to be treated. Such an arrangement provides exceptional versatility and control over the beam emitted. According to an another aspect, the aperture for a single laser source is rapidly changed during the performance of a procedure. By rapidly switching between forming an incision and cauterizing, an incision can be cauterized while being made.