Down syndrome (DS) is the most common chromosomal disorder. It is featured by intellectual disability and is caused by trisomy 21. People with DS can develop some traits of Alzheimer disease at an earlier age than subjects without trisomy 21. Apoptosis is a programmed cell death process under both normal physiological and pathological conditions. Poly (ADP-ribose) polymerase 1 is a mediator of programmed-necrotic cell death and appears to be also involved in the apoptosis. The aim of the present work was to detect the intracellular distribution of PARP-1 protein using immunofluorescence techniques and the expression of PARP-1 mRNA in culture of fibroblasts of DS subjects. The analysis of the intracellular distribution of PARP-1 show a signal at the nuclear level in about 75 % of the cells of DS subjects with a slight uniformly fluorescent cytoplasm. In contrast, in about 65% of the analyzed fibroblasts of the normal subjects only a slight fluorescent was found. These observations have been confirmed by PARP-1 gene mRNA expression evaluation. The data obtained from this study strengthen the hypothesis that the over-expression of PARP-1 gene could have a role in the activation of the apoptotic pathways acting in the neurodegenerative processes in DS.