Hair grows through the hair cycle consisting of anagen, catagen and telogen. We investigated the role of Sox13, a member of the Sox family of transcription factors that are involved in cell fate determination and differentiation, using Sox13 mutant mice. We found that Sox13 expression in hair follicle is dynamically changed during hair cycles, indicating that Sox13 is a novel hair cycle maker. Elucidation of the mechanism underlying the Sox13 cyclic expression would be important for understanding the pathogenesis of alopecia.