Objective: This study was designed to verify and quantify sensory dysfunction in a patient with benign idiopathic trigeminal sensory neuropathy. Design: Point-biometric case study comparing the affected site to the unaffected contralateral site. Setting: A physiologic pain laboratory. Patient: A 26-year-old man with right-sided facial numbness of unknown etiology. Interventions: Not applicable. Main Outcome Measures: A standardized battery that included mechanical detection threshold, temperature, vibration detection threshold, pressure-pain threshold, stimulus-response functions (brush, pinprick), temporal pain summation, and thermal quantitative sensory testing. Results: The patient's results revealed sensory differences between the affected right and the contralateral unaffected side of the face. The patient exhibited decreased sensation to mechanical stimuli on the affected side, with greater hypoesthesia in the ophthalmic (2.44 affected side vs 1.65 unaffected side) and maxillary (2.54 affected vs 1.65 unaffected) branches with no difference in the mandibular distribution. Vibratory sensation was also decreased on the affected side, particularly in the maxillary distribution (Reidel-Seiffer tuning fork: 8.0 affected vs 5.0 unaffected). The maxillary distribution showed a significant decrease in response to temporal pain summation on the affected side. A comparison of warm and cold sensation thresholds and cold-pain and heat-pain thresholds between the affected and unaffected ophthalmic branches revealed a significant side-to-side variation of cold-pain thresholds, indicative of cold-pain allodynia (hyperalgesia). Similar differences were found at the maxillary and mandibular branches, indicating cold-pain allodynia on the affected side in these distributions. In addition, there was moderate side-to-side heat-pain variation in the maxillary branch suggesting heat-pain allodynia. Conclusions: Trigeminal sensory neuropathy has the potential to affect a variety of sensory modalities. We found unilateral sensory changes in thickly myelinated Aβ fibers (touch, pressure, and vibration), thinly myelinated Aδ - fast pain fibers (temperature), and unmyelinated C - slow pain fibers (temperature).