The EMBO Conference on ‘Protein Phosphorylation and Protein Phosphatases’ was held in Marburg, Germany, July 8–12, 2001. The organizers were Susanne Klumpp (University of Marburg), Joaquin Arino (University of Barcelona) and Mathieu Bollen (University of Leuven). Next year the meeting will go to the USA. It will be organized by Ben Neel (bneel@caregroup.harvard.edu) and Angus Nairn and will be held at Snowmass, CO, July 13–18, 2002. The 2003 conference will be held in Europe again, at Sitges, near Barcelona, Spain, under the management of Joaquin Arino (joaquin.arino@uab.es), Susanne Klumpp and Denis Alexander. ![][1] According to a modest estimation, one third of the known eukaryotic proteins can be phosphorylated. Protein kinases are members of a large superfamily and incorporate the phosphate moiety into the serine (Ser), threonine (Thr) or tyrosine (Tyr) residues of their target proteins. In comparison, protein phosphatases are less numerous but more diverse. They can be classified into four independent protein families according to their substrate specificities, catalytic mechanisms and amino acid sequences (Figure 1). The phosphatases specific for Ser and Thr side chains were first identified in classical biochemical studies, but their subsequent cloning revealed significant structural differences between the family members, which led to their division into the phosphoprotein phosphatase (PPP) and metal‐ion‐dependent protein phosphatase (PPM) subfamilies. Molecular cloning and genetic studies also led to the discovery of the so‐called novel PPP enzymes. Despite the fact that both PPP and PPM subfamily members utilize the same binuclear metal assisted catalytic mechanism, they appear to have emerged through convergent evolution. Tyr‐specific protein phosphatases (PTPs) have been identified since and are composed of transmembrane (receptor‐like) and cytosolic (non‐receptor) subfamilies. These phosphatases not only counterbalance the effects of receptor and cytosolic protein Tyr kinases but also transmit information through the plasma membrane. Thus, they are of paramount importance in cellular … [1]: /embed/graphic-1.gif