Some 40 years has passed since poly(ADP-ribose) and the poly(ADP-ribosyl)ation reaction were discovered. Characteristics of poly(ADP-ribose) with a huge biopolymer with branching makes poly (ADP-ribosyl)ation a powerful post-translational modification of biological materials as well as a unique structural component of eukaryotic cell chromatin. Localization of poly(ADP-ribose) poly-merase (PARP-1) in the nucleus and its enzymatic activation by DNA strand break makes this modification an important mechanism of DNA repair and other reactions involved in DNA metabolism. However this reaction turned to be not confined in the nucleus but might be involved in the cytoplasmic events. Recent findings in our laboratory clarified that PARP-1 also localizes to the centrosome and the cells from knockout mice of PARP-1 shows several abnormalities related to the centrosome function. Involvement of poly(ADP-ribose) metabolism in regulation of neuronal cell function was also indicated. This review describes such recent findings suggesting the metabolism of poly(ADP- ribose) is very dynamic and important for maintenance of cell functions.