This bulletin summarises information collected in the fourth Census of statutory and non-statutory drug and alcohol treatment services in Northern Ireland to establish the number of persons in treatment for drug and/or alcohol misuse. The Public Health Information and Research Branch, within the Department of Health, Social Services and Public Safety, conducted the Census on 1st March 2012. The first Census was conducted on 1st March 2005, and was repeated on 1st March 2007 and on 1st March 2010.