Abstract: A force-controlled periodontal probe is disclosed, the probe having a scale-marked shaft slidably carried by an alignment sleeve at the head end of the instrument and urged into a normally extended condition by a thin leaf spring. Measurements of gingival sulcus depths are taken when the force applied by the periodontist to the handle of the instrument and the resistance to further penetration by the tip portion of the shaft have caused the shaft to shift into an indicated displaced position. In that position the spring exerts a predetermined and accurately reproducible probing force.