This report updates two separate analyses undertaken in 1998 and 1999 in Toronto and Vancouver respectively to develop current estimates of the relative cost of addressing homelessness across a range of responses. It also expands on the earlier analysis by adding data for two other cities, Montreal and Halifax. The primary research question examined is the relative cost of addressing homelessness through institutional and emergency response systems, such as psychiatric hospitals and treatment centres and emergency hostels and shelters compared to purposefully designed community based supportive and affordable housing.