Distal trisomy of 13q represent a clinical syndrome and has a higher frequency than proximal trisomy. Phenotype-karyotype correlations for partial trisomies of chromosome 13 are discussed more extensively than in most other partial trisomy syndromes. On the basis of the summary of published cases, one can conclude that orofacial clefts and scalp defects are caused by genes that are duplicated on the proximal portion of 13q. The prominent nasal bridge and polydactyly are caused by genes on the bottom half of 13q. Cases of partial 13q have a better outcome in terms of lifespan than full trisomy 13, suggesting that genes all along the chromosome are involved in the occurrence of increased neonatal mortality. We report a boy, 17 months with trisomy 13q3 and a typical phenotype for the trisomy of this region; lower birth weight, psychomotor retardation, trigonocephaly, hypotelorism, antimongoloid slant, long upwardly curved eyelashes, bushy eyebrows, synophrys, stubby nose, long philtrum, thin lip, ears with a small lobule and a prominent antihelix, capillary hemangiomata in nuchal region, unilateral postaxial polydactyly, bilateral simian crease. Echographic examination identified renal malformations (rudimentary ren sinister). The cytogenetic investigation revealed a duplication of q3 region of the chromosome 13. Karyotyping analysis with G and R-banding showed: 46,XY, der(13), dup q3; trisomy 13q3. The trisomy 13q syndrome arise usually from parental balanced translocations, sometimes from parental pericentric inversions, and rarely from de novo duplications. The cytogenetic examination of the parents resulted normal. The patient had de novo duplication resulted from the unequal crossing-over during the meiosis, so the risk of recurrence for patient's sib was not increased.