The roots of plants normally carry small hairs arranged in a regular pattern. Transfer DNA-tagged lines of Arabidopsis thaliana included a mutant with few, randomly distributed root hairs. The mutated gene CAPRICE (CPC) encoded a protein with a Myb-like DNA binding domain typical of transcription factors involved in animal and plant development. Analysis in combination with other root hair mutations showed that CPC may work together with the TTG gene and upstream of the GL2 gene, Transgenic plants overexpressing CPC had more root hairs and fewer trichomes than normal. Thus, the CPC gene determines the fate of epidermal cell differentiation in Arabidopsis.