In modern dairy farming, lactating cows and un-weaned calves are often housed indoors, in a restricted space, at high density, and/or separate from other animals. Such housing conditions affect the welfare of the animals by creating risks of illness and injuries and placing restrictions on behaviour. This chapter will examine issues arising from the physical and social aspects of dairy cattle housing, with a focus on the most current and controversial issues in the area. Sections 2–5 focus on the different housing systems available for lactating cows and on the advantages and disadvantages of these alternatives. Sections 6–8 then review the issue of housing for un-weaned calves.