Background: Recombinant Down Syndrome with partial duplication of the long arm of chromosome 21 represents a rare form of partial trisomy 21. The cause is mostly chromosome rearrangement- pericentric inversion of maternal or paternal homologous chromosome 21 and duplication of Down syndrome critical region p11.1q22.1, resulting in a child with phenotypical signs of classical Down syndrome with psychomotorical developmental delay. Methods: We describe a Down sydrome female infant with partial trisomy of chromosome 21. Ultra- sound screening for Down syndrome in the first trimester of pregnancy determined high risk for chromosomal abnormality. Amniocentesis showed normal prenatal karyotype. After birth a female infant started to show symptoms and signs, typical for classical Down syndrome. Postnatal karyotype revealed pericentric inversion and duplication of one chro- mosome 21 of maternal origin in the p11.1q22.1 region. The follow up of female infant up to three and a half years shows signs of psychomotorical delay with no structural defects. Therefore her developmental amelioration is less expressed compared to classical Down syndrome. Conclusions: Developmental follow up of a girl with partial trisomy 21 reveals a lot of similarities with the development of children with classical trisomy 21, but less expressed: facial gestalt, short statue, hypotonia and intellectual disabilities. Global developmental delay in spite of developmental treatment grows more and more evidently.