The invention relates to a method for regulating the average wavelength of a laser, especially a semiconductor laser, comprising a wavelength-selective, at least partially reflecting optical element (27) and being operated in a unimodal manner. The inventive method involves the following steps: a control variable influencing the optical resonator length (L.sub.opt) of the laser (29) over a pre-determined range is modified continuously or step-by-step; the characteristic of the optical monitoring power (P.sub.mon) which is influenced in this way and emerges on the side opposite the optical output of the laser (29), or the characteristic of a detection variable dependent on the optical monitoring power, is detected continuously or step-by-step; and the control variable influencing the optical resonator length (L.sub.opt) is regulated in such a way that a pre-defined value of the increase of the characteristic of the optical monitoring power (P.sub.mon) or the characteristic of the detection variable dependent on the optical monitoring power, is reached in a point inside the control variable range, or a pre-defined value of a functional dependence (F(dP.sub.mon/dL.sub.opt)) is reached, containing the increase of the characteristic of the optical monitoring power (P.sub.mon) or of the characteristic of the detection variable dependent on the optical monitoring power. Furthermore, the invention relates to a device for carrying out the inventive method.