: In the National Institute of Industrial Safety (NIIS), the information retrieval system concerning labour accidents has been developed. This developed system has been called as "SAFE II". The SAFE II consists of the data base of the Labour Accident Reports in JAPAN and the data base of the books/journals concerning labour accidents. The data base of the Labour Accident Report treats the information described on the first page of the Mission Reports on investigation of labour accidents by the Ministry of Labour. However, information items of the data base are often insufficient to investigate and analyze the causes of explosion and fire, therefore the subsidiary data base concerning explosions and fires has been constructed. This explosion/fire data base is based on summaries of Mission Reports on investigation of labour accidents concerning explosion and fire by the Ministry of Labour from 1955 to 1993 in JAPAN. The summaries have been made by NIIS staffs of Chemical Safety Research Division for more than 35 years. This document deals with the transition of the accidents and the relationship between frequency and magnitude of the accidents by using the explosion/fire data base. In this document, following results are shown,

1. The numbers of explosions/fires and injuries in 1990s are about half of these in 1960s. But the number of fatalities in 1990s is as almost same as the number in 1960s.
2. Decennial frequencies by month, day and hour decrease roughly in proportion to the decennial number of explosions/fires, and their component ratios are as almost same as other decades'.
3. The frequency of the explosions/fires in the chemical industry is lower than the total of others, but the damage of explosions/fires in the chemical industry is liable to be greater than others. Fireworks and explosive industry have high risk of death/injury of workers, when an explosion or fire occurs.
4. Explosions/fires caused by self-ignition have as almost same risk of death/injury of workers as explosions caused by explosives. These risks are higher than risks caused by steam explosions, dust explosions and gas explosions.
5. Between 1955-1964, the most frequent causative substance which caused explosions/fires was acetylene. Recently, these were liquefied petroleum gas (LPG) and organic solvent. The most frequent ignition source which caused explosions/fires was welding or cutting by electric arc or gas.

Keywords ; Labour accident, Data base, Explosion, Fire, Statistics, Frequency-magnitude curve, Causative substance, Ignition source