The recording of physiological data on the magnetic tape is suitable 1) when automatical analysis of the experimental data should be performed in another laboratory or 2) in field research, when the transfer of an appropriate recorder or analyser is difficult. — Various possibilities of the use of magnetic recording, especially in the occupational physiology and hygiene, are discussed. “Direct recording” of the physiological data (on a conventional tape recorder, designed for recording of sound) is possible only for some kinds of signal, e.g. the E.M.G. or action potentials of nerve and muscle cells or fibres. When signals, including frequency components in the range of several c/s are to be recorded (e.g. the E.C.G. or E.E.G.), it is necessary to use a modulated carrier frequency for recording. Technical parameters of various modulation systems of recording are compared. The requirements on a system of recording for research in work physiology and hygiene are proposed. — In the second part of the paper a transistorized frequency modulator (carrier frequency 5000 c/s, frequency deviation ± 40%) and a transistorized demodulator are described. In connection with a small conventional magnetic tape recorder they enable to record a signal in the frequency range 0.5–800 c/s ensuring the signal-to-noise ratio more than 50:1; examples of records of E.E.G., E.M.G. and E.C.G. are presented.