Salmon patch is commonly seen on the nuchal area, glabella, or eyelids of newborn infants as a pink to deep scarlet patch, due to teleangiectasia in the dermis. The same skin changes are seen in portwine stains. Salmon patches always appear symmetrically in contrast to a unilateral distribution of portwine stain. The biggest difference appears in the course of the lesion; the salmon patch tends to fade away but portwine stains persist. The incidence, however, and prognosis of salmon patch are not clear. We examined people of all ages to see how many had a salmon patch. We examined 5054 Japanese people attending clinics at Hirosaki and Yamagata Universities from 1987 to 1997. There were 162–216 at each year under 14 years old, 265 between 15–19 years old, and 287–433 at each decade over 20 years old. There were roughly the same number of males and females. 82% of children up to 1 year old had a nuchal salmon patch. This percentage decreased and at the age of 9, it was 4·5%. These results are concordant with Smith and Manfield and Leung et al who described high incidences of nuchal salmon patch in the newborn and a subsequent decrease. 92% to 6% and 45% to 0%, respectively. However, they could not explain the high incidences of 20% to 50% in adults, which had been reported by the authors who had investigated the adult population. In our study, the incidence of nuchal salmon patch gradually increased from the age of puberty to the 20s, rising to 31%, then stabilised at 26–39% in older age groups. Our results indicate that nuchal salmon patch fades away but can reappear. This is also the case with facial salmon patch; the incidence in the present study was 18% in newborns, 0·02% in school children, and 3·5% in adults over 40 years (data not shown). The mechanism of fading and reappearance of a salmon patch is unclear. One explanation may be an effect of sex hormones. Vascular endothelial cells possess specific receptors for oestrogen, and several teleangiectatic conditions of the skin such as vascular spider and red palm are seen in hyperestrogenic states such as pregnancy and liver cirrhosis.