The Social Housing Outcomes Worth (SHOW) study was established in 2003 in collaboration with Housing New Zealand Corporation to assess the relationship between housing conditions and health, particularly between household crowding and infectious diseases. The SHOW study measures health outcomes using linked anonymised hospitalisation and mortality records provided by the New Zealand Ministry of Health. By December 2011, the study population consisted of 11,196 applicants and 196,612 tenants. Half were aged <21 years. About two-thirds identified as Māori or Pacific ethnicity. Household incomes were low. Of tenant households, 44% contained ≥1 smokers compared with 33% for New Zealand as a whole. Whereas about 10% of New Zealanders are exposed to household crowding, as measured by a deficit of one or more bedrooms, about 52% of housing applicants and 38% of tenants were living in households with this level of household crowding.