Hair casts (HC) appear to have become more common in young adults. An investigation on the incidence of HC was made in the Chengdu district of China. Of 3548 individuals surveyed, 30.24% suffered from HC. HC were restricted to females, among whom the incidence was 61.6%. HC is thus a very common finding. Long-term and frequent traction imposed on hair with excessive force appears to be the major cause of HC. This was confirmed from braiding studies which consisted of traction by tightly drawn braids on healthy subjects, together with histopathology of the underlying skin and statistical data on the frequency of HC.