Philip Cohen, the Director of the MRC Protein Phosphorylation Unit, has reached a scientific milestone with the publication of his 500th paper. Last year, Philip was elected a Foreign Associate of the United States National Academy of Sciences, which allows him to contribute up to four papers a year to Proceedings of the National Academy of Sciences (PNAS). By a happy coincidence, his 500th research paper was his inaugural article for this journal, a paper in which his Ph.D. student Hilary Smith identified the phosphorylation sites on the E3 ubiquitin ligase Pellino that are critical for its activation by the protein kinases IRAK1 and IRAK4 (Smith et al (2009) Proc Natl Acad.Sci. USA 106, 4584-4590). Philip's first paper was published in 1968 when he was a graduate student at University College London and appeared in the first issue of the Volume 1 of FEBS Letters. Philip's "H index' is 124, which means that 124 of his papers have been cited over 124 times. According to the Institute for Scientific Information, Philadelphia, he was the world's second most cited scientist in the field of Biology and Biochemistry over the period 1992-2002.