Chromosome studies were performed on a plexiform neurofibroma arising in a probable von Recklinghausen's disease patient, who also showed a de novo constitutional reciprocal translocation, t(1;22)(p32;q11). Banding analysis of the metaphases obtained from two primary cultures in vitro showed the presence of five cytogenetic clones, characterized by different chromosomal rearrangements. In addition to t(1;22), marker chromosomes involved pairs 1, 2, 3, 5, 8, 9, 10, 12, 16, and X. These findings suggest a possible polyclonal evolution in this neurofibroma.