This article discusses how cultural concepts of marriage and reproduction play a primary role in how genetic disorders are regarded in Japan. The article examines the anxieties that accompany the taking of genetic tests in the context of Japanese cultural concepts of family, care and genetic disorders. The analysis draws on data from two studies conducted over two years (2006–2008), based on semi-structured interviews with individuals affected by a genetic disorder, and a study of prenatal decision-making as regards the taking of tests during pregnancy, which also involved interviews with medical professionals, including certified clinical geneticists, genetic counsellors and scholars. A number of studies, as well as governmental documents, have emphasized the importance of respecting culture in dealing with a genetic disorder and genetic information. Though we regard respect for culture as important, we show that respect for culture might hide superstitions and culturally embedded prejudices about genetic disorders. We show this by analysing the given motivations of couples for taking a genetic test and by tracing the ways in which ‘genetic information’ is understood in a socio-cultural context.