A panning stereo endoscope which maintains an up-down orientation as the stereo endoscope pans an operative field, the panning stereo endoscope comprising: a shaft having an axis; first and second optical channels extending along the shaft, each of the first and second optical channels having an off-axis direction of view; and an actuating mechanism carried by the shaft and adapted to (i) synchronously rotate the first and second optical channels about their respective axes, and (ii) synchronously, inversely piston the first and second optical channels along their respective axes, wherein the actuating mechanism comprises: - first and second spur gears , which are fixed to the first and second optics tube assemblies , such that turning spur gears causes optics tube assemblies to turn - a ring gear which engages the two spur gears , wherein the ring gear is secured to a face cam , which is contoured to provide one complete proximal-distal reciprocating excursion of optical tube assemblies for each complete revolution of their respective spur gears - an inner face cam follower and an outer face cam follower , wherein each cam follower has two follower points , with each follower point being set 180 degrees from the other follower point on a given cam follower and wherein the two follower points of one cam follower are offset 90 degrees from the two follower points of the other cam follower. a shaft having an axis; first and second optical channels extending along the shaft, each of the first and second optical channels having an off-axis direction of view; and an actuating mechanism carried by the shaft and adapted to (i) synchronously rotate the first and second optical channels about their respective axes, and (ii) synchronously, inversely piston the first and second optical channels along their respective axes, wherein the actuating mechanism comprises: - first and second spur gears , which are fixed to the first and second optics tube assemblies , such that turning spur gears causes optics tube assemblies to turn - a ring gear which engages the two spur gears , wherein the ring gear is secured to a face cam , which is contoured to provide one complete proximal-distal reciprocating excursion of optical tube assemblies for each complete revolution of their respective spur gears - an inner face cam follower and an outer face cam follower , wherein each cam follower has two follower points , with each follower point being set 180 degrees from the other follower point on a given cam follower and wherein the two follower points of one cam follower are offset 90 degrees from the two follower points of the other cam follower. - first and second spur gears , which are fixed to the first and second optics tube assemblies , such that turning spur gears causes optics tube assemblies to turn - a ring gear which engages the two spur gears , wherein the ring gear is secured to a face cam , which is contoured to provide one complete proximal-distal reciprocating excursion of optical tube assemblies for each complete revolution of their respective spur gears - an inner face cam follower and an outer face cam follower , wherein each cam follower has two follower points , with each follower point being set 180 degrees from the other follower point on a given cam follower and wherein the two follower points of one cam follower are offset 90 degrees from the two follower points of the other cam follower. <EOS>