A syndrome of deep pain in the breast during and immediately after lactation has been ascribed to an infection with Candida albicans. A series of 20 patients with deep pain, another 20 with superficial infection and 20 healthy women were compared with respect to the growth of bacteria and fungi. C. albicans was found twice as often in the milk of women with superficial lesions compared to those with deep pain. Bacteria were often found on the nipple and in the milk of those complaining of deep pain. Thus, if the deep pain syndrome is caused by microbes, this study points to a pathogenic role of bacteria rather than fungi.