A surgical device for use with an endoscope to perform gastroesophageal hemostasis operations on bleeding gastroesophageal varices and for forceful esophageal dilation to correct achalasia comprises an insertion member, an inflatable balloon, an attachment component in the form of a substantially thin-walled elongate tubular sheath made of a flexible material for removably attaching the balloon in a collapsed configuration to the endoscope insertion member, and an inflation device operatively connected to the balloon for enabling an expansion of the balloon from the collapsed configuration to an expanded configuration. The sheath is provided along its length and on an outer surface with a distance scale to enable the positioning or alignment of the balloon with the desired surgical site in cases where the endoscope protrudes from the distal end of the sheath and is therefore staggered by a predetermined distance with respect to the balloon. Alternatively or additionally, the balloon is transparent and at least a portion of the sheath in a region about the balloon is transparent. In this case, the distal end of the endoscope is preferably aligned with the balloon. Once the desired surgical site has been located visually through use of the endoscope, the distal end of the endoscope's insertion member being juxtaposed to the surgical site, the balloon is inflated.