Aims: To use simple thermal devices with different diameters and temperatures to investigate reliability and magnitude of human intraoral thermal sensitivity. Methods: Sixteen healthy volunteers participated. Six thermal devices with tapered circular ends (stimulus diameter 3, 5, and 10 mm) were used. Three different temperatures (room temperature, heat, and cold) were applied with each of the three diameters, ie, nine combinations. Participants were stimulated in randomized order at nine different sites: tongue, lip, maxillary attached gingiva adjacent to the left and right central incisors (without touching the lip) and to the left and right premolars (with or without touching the lip), and the left and right cheeks extraorally. Participants rated the perceived stimulus intensity on 0-50- 100 numeric rating scales (NRS). The number of paradoxical thermal sensations was also recorded. Ten volunteers were examined twice on the same day and recalled for a second session for assessment with the 5-mm-diameter device of within- and between-session reliability (interclass correlation coefficients [ICC]). The results were analyzed using a three-way analysis of variance. Results: Reliability of NRS scores ranged from poor (ICC = 0.09, with cold stimulation at the premolar region) to excellent (ICC > 0.92, with cold stimulation at the cheek or tongue). NRS values varied with stimulus diameter (P .050), temperature (P .001), and sites (P .001), with significant size × site and temperature × site interactions (P .001). The tongue was the most sensitive site (P .001) and the gingiva was the least sensitive site (P .050). The 10-mm-diameter device produced higher NRS scores than the 3-mm-diameter device. Conclusion: The reliability of intraoral thermal sensitivity recorded with the 5-mm-diameter device varied greatly between different sites. Nonetheless, with this caveat in mind, the study did document that semiquantitative assessment of intraoral thermal sensitivity is feasible and applicable for clinical studies in different intraoral pain conditions. Keywords: intraoral, quantitative sensory testing, somatosensory sensitivity, thermal