Abstract: An endoscope having a longitudinally-slotted probe that is connected to a guidance part for an optical system which extends in an axially movable fashion through the guidance part into the probe and the view of which is directed toward the longitudinal slot of the probe. The axial adjustment of an associated optical system is operated by a drive, which is connected to the guidance part and can be operated by hand. The instrument can be held by an operator using one hand and, as this is done, the optical system can be securely brought into position. The optical system can be adjusted using this same hand, thus permitting the operator to use the other hand to guide a surgical instrument.