The invention relates to a system for medicinal treatment, in particular for treating benign prostatic hyperplasia BPH, for use in the event of tumor resection or for use in thoracic surgery. The system comprises a diode laser device for producing a laser beam and to an application system based on optical wave guides that can be endoscopically introduced into a patient. Said system is designed in such a manner that the laser beam, produced by the diode laser device is guided through the application system and is emitted by said application system so that biological tissue can be treated in a selective manner with the emerging laser beam.