Attempts were made to compare the circadian rectal temperature rhythm between 5 blind and 5 sighted subjects. Rectal temperature was measured continuously for 24 h, at an ambient temperature of 28°C and a relative humidity of 60%, in the resting subject. The difference between the maximum and the minimum values of the rectal temperature (= range of oscillation) was 0.82 ± 0.09°C (mean ± S.E.) and 0.91 ± 0.11°C, and the 24‐h mean of rectal temperature 36.88 ± 0.22°C and 37.03 ± 0.14°C in the blind and the sighted subjects, respectively. These values between the two groups were not significantly different. The morning rise of rectal temperature began at ca. 3 a.m. in the sighted subject, but did not occur until at least 6 a.m. in the blind subject. The evening fall of rectal temperature also seemed to occur at later times in the blind subject. Our present findings suggest that the reduction of the ability to sense light and dark in the blind subject delays the phase of the rectal temperature rhythm, but it does not change the circadian pattern and the range of the oscillation in the rectal temperature rhythm. These findings are discussed from the viewpoint of circadian physiology.