The assertion that where crimes take place is to a large extent determined by physical lay-out has been made forcibly by Oscar Newman in 'Defensible Space', where particular attention is given to the problem of high rise developments. Here, data from a Sheffield survey has been used to test whether area crime patterns do vary with design features. Some differences were found, but these by no means showed high rise flats to be at a disadvantage. To reconcile these results with Newman's, the concept of 'defensible space' was analysed in some detail. It seemed that the concept was so wide that many designs could incorporate both good and poor defensible space qualities, and a more rigorous definition was recommended.