Adenosine 5'-diphosphate (ADP)-ribosylation is a protein posttranslational modification that is catalyzed by ADP-ribosyltransferases (ARTs), using nicotinamide adenine dinucleotide (NAD(+)) as a substrate. Mono-ribosylation can be extended into polymers of ADP-ribose (PAR). Poly(ADP-ribosyl)polymerase (PARP) 1, the best-characterized cellular enzyme catalyzing this process, is the prototypical member of a family of mono- and poly(ADP-ribosyl)transferases. The physiological consequences of ADP-ribosylation are inadequately understood. PARP2010, the 18th International Conference on ADP-Ribosylation, attracted scientists from all over the world to Zurich, Switzerland. Highlights from this meeting include promising clinical trials with PARP inhibitors and new insights into cell, structural, and developmental biology of ARTs and the (glyco)hydrolase proteins that catalyze de-ADP-ribosylation of mono- or poly-ADP-ribosylated proteins. Moreover, potential links to the NAD-dependent sirtuin family were explored on the basis of a shared dependence on cellular NAD(+) concentrations and the relationship of ADP-ribosylation with intermediary metabolism and cellular energetics.