In the last five years increasing interest has been shown in the use of radio-tracking systems in field investigations. Several workable tracking facilities have been developed and used in various projects. The paper reviews accounts pertaining to the use of telemetry in field studies. In addition, brief mention is made of the author’s use of biotelemetry in avian navigation studies. These systems are designed to enable investigators to record data (e.g., spatial position, body temperature, heart rate, etc.) about animals roaming free and under natural conditions without being under direct observation. The several disadvantages (cost, added complications, lack of units for smaller species, inadequate range, etc.) of the existing equipment fail to distract from its realized or potential value in biological research. Any impression that biotelemetry is a means for solving all field problems, and therby making other techniques obsolete, is erroneous. Biotelemetry is simply another tool that will enable biologists to obtain new data for formulating answers to their many questions.