The Great Soviet Encyclopedia defined eugenics as “a reactionary pseudo-science popular in capitalist countries that aims to improve ‘the human race’” (GSE 2nd ed. 1952). However, as a number of studies have demonstrated (e.g. Paul 1984, Adams 1991, Mocek 1998), eugenics was a “science” embraced not only by reactionaries and capitalists, but a large number of leftists as well, partly because it was often thought to have the potential to solve various problems in society.

Some representatives of Japanese left wing spectrum, particularly those involved in birth control activism, also showed interest in eugenics, some embracing it as a path to happiness, others criticizing its coercive aspects but approving of ”voluntary” (or, as it is often called nowadays “liberal”) eugenics. There were also those who denied it altogether. The aim of this paper is to analyze Japanese left-wingers view of eugenics, trying to find out what solutions for the working class they were (or were not) seeking in eugenics.