The variegated mutant P 17 characterized by the presence of dicentric chromosomes was induced by X-irradiation of pollen with 750 R. This dicentric chromosomes is persistant and transmissible; both centromeres are active and the intercentromeric region is long enough to allow the formation of criss-cross and parallel double bridges. Mitotic behaviour of the dicentric chromosome determines a mixochimeric structure wich causes a mosaic phenotype pattern. Associations of the dicentric with more than two chromosomes at metaphase I shows that the dicentric chromosome is heterodicentric.