Over the last 10 years, it has become apparent that poly-ADP ribosylation reactions govern some of the fundamental processes of life. PARP 1 is a highly conserved enzyme and a constitutive factor of the DNA damage surveillance network and plays an essential role in the protection andprocessing of DNA ends as they arise in DNA damage, repair, and recombination. The recent discovery of multiple members of the PARP family suggests an expanded role for poly-ADP ribosylation reactions. Poly ADP-ribosylation Reactions contains basic knowledge of poly-ADP ribosylation reactions andreviews the most recent molecular (including the crystal structure) and genetic (including knock out mice) approaches that have contributed to our understanding of the physiological role PARP 1 and its homologues. A discussion of the novel pharmacological role of inhibition of PARP is also included.The final chapter outlines future directions in the field of cellular responses to DNA damage. Its comprehensive coverage of the multiple aspects of this type of post-translational modification induced by DNA damage mean this book will serve as reference for both new and experiencedinvestigators.