An infrared data transmission and reception system capable of avoiding adverse effects due to infrared external noises includes a data transmitting circuit and a data receiving circuit of which the former is so constructed as to add a signal-free region of a predetermined length or a trailer to the terminating end of each of the frames of a data bit pulse train and the latter is so constructed as to discriminate between transmitted data and external noise by detecting whether or not the region corresponding to the trailer is signal-free with respect to a detected output, whereby a proper encoding output is generated on the basis of the discrimination.