This paper examines the factors involved in working with 'hard to reach' homeless drug users. The author uses the example of Merchant Quay Ireland's Outreach Service, which seeks to work with people who are marginalized, isolated, socially excluded and highly mobile. Included under the general description 'hard to reach' are the following: younger chaotic drug users; homeless drug users; female drug users; drug users from ethnic minorities; homeless people and drug users; rough sleepers; and, homeless youths. Despite the obstacles faced by MQI's drugs outreach team, the author concludes that outreach is an effective strategy in dealing with 'hard to reach' populations. However, there is a clear need for relevant agencies to support new initiatives such as the establishment of a wet hostel, alternative treatment options, and increasing the number of places on current treatment programmes.