Cytological and clinical observations have been presented from an abnormal human female who exhibited two chromosomally distinguishable cell lines in composition. One of her cell lines conformed with 46, XX chromosome types. On the other hand, the second cell line consisting of 47 chromosomes per cell had two unequal aberrant meta-centric chromosomes that had replaced a regular C-group autosomes. It is interpreted that these aberrant chromosomes are the isochromosomes that arose from the missing C-autosome. Since, the isochromosomes for both arms of this autosome were retained by the patient, this has produced the phenotypic features of a trisomy.