In a factory involved in heavy industry, an investigation of noise levels was carried out; measurements were made of environmental noise, a questionnaire was given to the workers, and their hearing was tested with audiometer. The subjects were 795 male workers, 47.7 +/- 8.8 years of age (Mean +/- SD). There are many noisy machines in the factory: airblowers, sanders, steel-presses etc. Some of these put out high noise levels in operation, over 100dB (A) near the laborer's ear. About 60 percent of the laborers were working in a noise level below 85dB (A). Some are in the area of 85-90dB (A). There are a few laborers at the area over 90dB (A). The laborers had the following complaints: hearing loss (about 30 percent), tinnitus (15 percent), and dizziness (10 percent) etc. Hearing levels with 6 divided estimation method of many laborers were 15 to 19dB (25 percent) and 20 to 24dB (24 percent). Hearing levels become higher with aging. The group over 35 years of age showed higher hearing levels at sound frequency 4000Hz, i.e. such as c5 dip phenomenon. Most laborers are using ear plug, but some use them only occasionally. More industrial hygiene education should be given the laborers; routine noise measurements and regular medical checkups are needed.