Simple, inexpensive thermal stimulators—Minnesota Thermal Disks—have been designed based on the differences in heat transfer of copper (C), stainless steel (S), glass (G), and polyvinyl chloride (P). In healthy persons, C and P almost always can be recognized as “cold” and “warm,” respectively. The difference between C and S can be recognized only slightly (but significantly) better than by chance, and recognition of the difference between C and G is about halfway between that in the other two tests. Measurements on the forehead, hand and foot of 30 healthy persons of various ages showed evidence of decreased thermal discrimination with increasing age and of a difference in discrimination at various cutaneous sites.