The authors try to answer to some practical questions concerning Yag Lasers in neurosurgery. The aim of this work is to determine the main data useful for the choice of a YAG-Laser. Are considered: the wavelengths which can be bought on the international market (1.06 microns or 1.32 microns for instance), the peripherics at disposal, the tissular effects due to the different lasers, the surgical applications and indications. The Laser unit which will be chosen should be a compromise between the different advantages and inconveniences of a particular laser, its tissular effects, its price. The multi-wavelengths units appear to be, at the present time, interesting compromises (such as 1.32 + 1.06 microns, CO2 + 1.06 microns).