Maurice Raynaud first described the vasospasm of arterioles in 1862, and Raynaud's phenomenon is now felt to be common, affecting up to 20% of women of childbearing age. Raynaud's phenomenon has been reported to affect the nipples of breastfeeding mothers and is recognized by many lactation experts as a treatable cause of painful breastfeeding. In 1997, Lawlor-Smith and Lawlor-Smith reported 5 women with Raynaud's phenomenon associated with breastfeeding, but there are few other case reports, and none report the possible relationship between Raynaud's phenomenon of the nipple and previous breast surgery. We report 12 women who breastfed 14 infants, all of whom were seen in 1 pediatric practice and 1 lactation consultation center in San Francisco, California, within the past 3 years. Of the 12 women, 11 were seen between June 2002 and May 2003. All women suffered from extremely painful breastfeeding, with symptoms precipitated by cold temperatures and associated with blanching of the nipple followed by cyanosis and/or erythema. Poor positioning and poor attachment or latch may cause blanching of the nipple and pain during breastfeeding, but 10 of the 12 mothers were evaluated by experienced lactation consultations, who were sure that inappropriate breastfeeding techniques were not contributing factors. Because the breast pain associated with Raynaud's phenomenon is so severe and throbbing, it is often mistaken for Candida albicans infection. It is not unusual for mothers who have Raynaud's phenomenon of the nipple to be treated inappropriately and often repeatedly for C albicans infections with topical or systemic antifungal agents. Eight of our 12 mothers and their infants received multiple courses of antifungal therapy without relief before the diagnosis was made. To diagnose Raynaud's phenomenon accurately, additional symptoms such as precipitation by cold stimulus, occurrence of symptoms during pregnancy or when not breastfeeding, and biphasic or triphasic color changes must be present. All our mothers experienced precipitation of symptoms by cold stimuli and demonstrated biphasic or triphasic color changes, and 6 of the 12 experienced symptoms during pregnancy. Interestingly 3 of 12 mothers also reported a history of breast surgery, including 1 mother who had a fibroadenoma removed and 2 who had breast-reduction surgery. The association between breast surgery/implants and autoimmune disease, including Raynaud's phenomenon, has been discussed extensively, but the association of Raynaud's phenomenon of the nipple during breastfeeding has not been reported previously. Given the small numbers in the study, it is uncertain as to whether this may be a precipitating factor in developing Raynaud's phenomenon. Treatment options include methods to prevent or decrease cold exposure, avoidance of vasoconstrictive drugs/nicotine that could precipitate symptoms, and pharmacologic measures. There are reports in the lay press of the use of herbal medicines, aerobic exercise, and dietary supplements, but because most women with painful breastfeeding require immediate relief of the pain to continue breastfeeding successfully, it is important to offer a treatment plan that will alleviate the pain quickly. Nifedipine, a calcium channel blocker, has been used to treat Raynaud's phenomenon because of its vasodilatory effects. Very little of the medication can be demonstrated in breast milk and thus is safe to use in breastfeeding mothers. Of the 12 mothers in our series, 6 chose to use nifedipine, and all had prompt relief of pain. Only 1 mother developed side effects from nifedipine. Pediatricians and lactation consultants should be aware of this treatable cause of painful breastfeeding and should specifically question their patients, because most mothers will not provide this information to the breastfeeding consultant. Prompt treatment will allow mothers to continue to breastfeed pain free while avoiding unnecessary antifungal therapy.