To investigate unusual secular trends in suicide rate in Japan since the Second World War, the cause-specific mortality by sex and age during the period 1950-82 was analyzed. The results indicated that: suicide death rates due to two causes, i.e., poisoning by solid and liquid substances and run over by train and other means, for young persons increased remarkably in the mid 1950s; and the rates due to most causes for middle-aged men continued to increase during the period of economic depression following the oil crisis in 1973. The effects of availability of suicide methods and changes in economy on suicide death rate are discussed in the light of these findings.