The working hours per week in Japan have been usually held the system of 48 working hours and one holiday. Recently, in some enterprises, it has been setting the system of two holidays per week. It is interesting to observe the influences of prolonged holidays on worker's health. In this paper, auditory thresholds were investigated from the standpoint of the biological responses in workers to the prolonged absence from their working environments. The study was made on 19 male workers aged from 16 to 20. Their noise exposure varied between one and three years, but their clinical signs and audiograms were considered to be otologically normal. The noise rating number (N.R.N) in their workshop was 90∼105. They took one or two holidays per week, i.e. if they had taken one holiday in a specified week, they had to take two holidays in the next week. Audiometric examinations were carried out in the Saturday morning, and in the next Monday morning after one holiday. In the case of two holidays, examinations were carried out on Friday and the next Monday. The duration of the absence from noise was 40 hour in the former case, and 64 hours in the latter. Results were as follows. 1) The mean Monday morning thresholds after one holiday were lower at 1000, 2000 and 4000 cps. than those on Saturdays. 2) The mean Monday morning thresholds after two holidays were lower at 1000, 2000, 4000 and 8000 cps. than those on Fridays. 3) The differences between thresholds at the weekend and on the next Monday were greater at 2000 and 4000 cps. in the case of two holidays than in that of one holiday. 4) The Monday morning threshold after two holidays was lower only at cps. than that after one holiday. The above-mentiond results showed that the influence of the prolonged holidays on the auditory threshold was seen mainly at 4000 cps. It seems that this decrease of the threshold was brought about by the recovery of TTS during the prolonged absence from noise exposure.
