Mole rats (Spalax ehrenbergi) are blind, normally solitary, subterranean rodents found in southeast Europe and throughout the Middle East. Animals in Israel were captured in their burrows and maintained in laboratory cages for direct observation. They were found to be highly vocal, especially during physical encounters with each other. Their vocal repertoire consists of at least six call types, each occurring in a different behavioral context. The energy in all of the signals is below 8 kHz; some of the calls have most of their energy below 1 kHz. The temporal and spectral characteristics of these signals suggest that vocalization plays an important role in the subterranean life of the mole rat. [Supported by the National Science Foundation.]