A woman's build and the risk of breast cancer seem to be related. While relative overweight, as described by the body mass index, seems to be associated with increased breast cancer risk in postmenopausal women, overweight in premenopausal women seems slightly protective. Papers from a MEDLINE search are reviewed regarding the association between build and the development of breast cancer. Different aspects of build, such as height, weight, body mass index and body shape, are discussed. The more prominent associations found through this search are a positive association between height and breast cancer risk both in pre- and postmenopausal women. Regarding body mass index, the association is negative in premenopausal women and positive in postmenopausal women. Body shape described as masculine versus feminine seems to have no impact on breast cancer risk in premenopausal women, but seems to be positively associated with breast cancer in postmenopausal women. Possible biological mechanisms responsible for the associations with breast cancer risk are discussed, including endogenous oestrogens, androgens and glucose metabolic substances. Avoiding or reducing postmenopausal overweight may modify breast cancer risk indicators in a more favourable direction.