The investigations of the physical properties of magnetic ions diluted in metallic matrices with their local magnetic moments (if formed) coupled to the conducting carriers by s-d exchange interaction have led to several outstanding experimental and theoretical discoveries. These include, in particular, the Kondo effect, the Anderson virtual bound state (VBS) model, the Ruderman-KittelKasuya-Yosida (RKKY) indirect exchange interaction via free carriers, and the formation of metallic spin glasses. Since the very beginning, electron paramagnetic resonance (EPR) was used as an experimental tool to study these systems. In the pioneering works of Owen, Dyson, and Yosida [1‐ 3] the basic ideas of EPR on local moments in a conducting matrix were developed and quantified in the phenomenological Bloch-Hasegawa equations as reviewed, e.g., by Barnes [4]. One of the standard effects anticipated in these works is the carrier concentration induced shift of the position of the EPR resonance field of the local magnetic moment —the analog of the well known Knight shift in nuclear magnetic resonance. This effect can be expressed as a change of the local moment’s g factor: Dg › JsdrsEFdge, where Jsd is the local moment ‐ conducting carrier exchange integral, rsEFd is the density of states at the Fermi level EF , and ge is the g factor of conducting carriers. The change of the g factor is accompanied by the Korringa contribution to the width of the resonance line: DH › spy ¯ h df JsdrsEF dg 2 kBT with a characteristic linear temperature dependence. The Korringa contribution to the EPR linewidth was identified in a large number of diluted magnetic metallic systems [4] including semimagnetic semiconductors [5 ‐ 9] with both Mn 21 as well as Gd 31 , Eu 21 , and Fe 31 ions. The observation of the carrier concentration induced shift of the resonance field is quite rare and, in fact, is well documented only in strongly paramagnetic metals like Pd:Gd [4]. The experimental observation usually made is to find the resonance at a position different than expected for a given magnetic ion in other (nonconducting) matrices and assign the difference to the effect of the Knight shift. Also, in metals, a direct experimental proof by the observation of the carrier concentration induced shift scaling with the density of states at the Fermi level is not possible because of the inherent lack of control of the concentration of carriers. In this Letter we will show for the first time that a straightforward proof for the EPR Knight shift can be established for diluted magnetic systems with well controlled semimetallic electron properties. By changing the concentration of carriers in PbTe:Mn 21 , a strongly degenerated IV-VI semiconductor, we observe the shift of the resonance field being of different sign for holes and for electrons and scaling as a density of states at the Fermi level. This first observation of the EPR Knight shift in semimagnetic semiconductors gives new possibilities to determine experimentally both sign and magnitude of the Jsd exchange integrals. The method is unique in its ability to provide the information in the limit of strong dilution. It also has no limitations brought about by the high mobility required in the (usually applied) magneto-optical methods, so it is, in particular, suitable for disordered systems.