A radiotelemetry system for continuous monitoring of the temperature and/or location of small animals is described. All the functions of system control are carried out by an on-line microcomputer (TRS-80 Model II!), resulting in a versatile system capable of alternating recording the temperaturellocation of multiple subjects with other behavioral or physiological events, such as activity level. We describe the use of this system in monitoring body temperature in hamsters and in recording the incubation pattern of breeding ring doves.