Japan is a country strongly associated with strong, long-term relationships, whether they be located within kin- groups, local communities or large industrial enterprises. Yet Japan also has a long tradition of people who have been excluded from these relationships, whether voluntarily (hermits, mendicant monks, etc.) or compulsorily (outcasts etc.). This thesis deals with a contemporary category of people who operate largely outside the certainties of long-term relationships: day labourers. Whereas Japanese industry has become famous for 'life-time employment', my subjects often work under contracts for just one day. Most of them are also excluded from family and mainstream community life, living singly in doya-gai -- small urban districts with cheap hotels which resemble the American skid-row. These districts center on a casual labour market (yoseba), divided between a formal sector (public casual labour exchanges) and an informal sector (jobs negotiated on the street with recruiters often affiliated with yakuza gangs). Fieldwork (1993-5) was conducted mainly in Kotobuki, the Yokohama doya-gai, with brief field-trips to similar districts in Tokyo, Osaka, Nagoya, Kitakyushu and Fukuoka. Most of my informants were Japanese nationals, though Koreans and Filipinos are also briefly discussed. The thesis describes the lives and attitudes of day labourers, and the social organization of the very distinctive districts which they inhabit. Based on participant observation, backed up by historical analysis and cross-cultural comparison, the thesis considers the role of these 'men of uncertainty' in a society which craves certainty. In economic terms, that role is to enable the construction and longshoring industries to adjust to fluctuating demand and changing weather conditions while maintaining a stable core workforce. But day labourers, like other stigmatized minorities, have a parallel cultural role, as an "internal other" in the formation of mainstream Japanese people's identity