Dogs can be held temporarily or permanently in kennels for a number of reasons, not necessarily for their own benefit. Although restrictive environments have been associated with poor welfare, priorities for research and change cannot be understood unless the various aspects of the kennel environment are appreciated separately. This review critically evaluates the experimental research regarding the physical, social, sensory, occupational, nutritional and psychological aspects of the kennel environment and their effects on canine welfare, with a view to providing a consolidated report on our current state of knowledge on this subject. However, the lack of within-dog, single manipulations and a focus on quantitative measures affects the ability to make valid conclusions about the welfare benefits of several aspects, including social housing, kennel size and location. Despite these criticisms, the evidence for the positive benefits of group housing is strong. There is also considerable evidence for the benefits of positive human contact particularly on sociability and stress responses in other situations. Surprisingly few studies have looked at other forms of enrichment and even less have considered the potential for the kennel to be over-stimulating in an auditory, olfactory and visual sense. Such topics are suggested as priorities for further research, in addition to ways of minimising aggression in group housing and the effect of establishment of predictability on adjustment to kennelling.