The invention relates to a laser system for the treatment of body tissue (1) on an inner circumferential tissue surface (2). The laser system comprises a laser source (1) for the generation of a laser beam (3) and a handpiece (4) with a treatment head (5). The treatment head (5) extends along a longitudinal axis (6) and is adapted in an manner, that the longitudinal axis (6) of the treatment head (5) during operation is at least approximately parallel to the inner circumferential tissue surface (2). During operation the laser beam (3) enters the treatment head (5) in the direction of the longitudinal axis (6). A deflection mirror (7) is disposed in the treatment head (5) and guides the laser beam (3) radially outwards out of the treatment head (5) onto the inner circumferential tissue surface (2). Movable deflection means (8) for the laser beam (3) are provided to scan the inner circumferential tissue surface (2) within a treatment area (9) at least in a circumferential direction.
