Nest-boxes and nesting materials were considered potentially useful items with which to enhance the environment of rats housed in standard laboratory cages. This study was carried out to determine whether such items are actually used by rats, and if so, what features are important in their design. Laboratory rats were allowed to choose between four commercially available nest-boxes. Nest-boxes were preferred to other parts of the cage but the nest-box most frequently selected was not suitable for routine laboratory use. Accordingly a new nest-box was designed, incorporating features apparently attractive to the animals. This was a simple structure of opaque perspex, consisting of a roof and three walls. Similarly, rats were exposed to six commercially available nesting materials and those consisting of long paper strips were most preferred.