Temperatures can be obtained from small animals by implanting commercially available radio-telemetry probes (Mini-Mitters), thereby avoiding handling-induced artifacts. We have developed an inexpensive microcomputer interface to automatically collect data from Mini-Mitters. The interface hardware detects the signal and converts it to a TTL pulse train compatible with the Commodore PET microcomputer. The software converts the frequency to temperature, controls the sampling schedule, and can selectively measure any one of eight cages. Temperature measurements can thus be made around the clock with no technician present.