Forty one male workers employed in an underwater construction field were surveyed in the viewpoints of epidemiological analysis of decompression sickness (caisson's disease). Nineteen out of the entire forty one workers have been, or had been suffering from decompression sickness (as 46.3% of incidence rate) after decompression. The results obtained were as follows: 1. There was a significant relation between duration of work and incidence of disease. 2. Type II (severe type) comprised majority of cases (16 cases, 84.2%) despite any significant correlations were not present between severity types and recompression times. 3. Most frequently cited symptoms were lower limb pain (89.5%), upper limb pain (79.0%), pruritus (68.4%) and so on, however, 10% of patients complained of neurological symptoms. 4. There were not any significant correlations between incidence and worker's age or relative body weight.