Chen is Emeritus Professor at the National University of Singapore. He was Tan Chin Tuan Centennial Professor (2006-12), Distinguished Professor (2013-15), and served as Director, Institute for Mathematical Sciences (2000-12). He was President, Bernoulli Soc. for Mathematical Statistics and Probability (1997-99), President, Inst. of Mathematical Statistics (2004-05), and Vice-President, International Statistical Institute (2009-11). He has done fundamental work on Poisson approximation, now known as the Chen-Stein (or Stein-Chen) method. His research in discrete probability has broad applications ranging from molecular biology to probabilistic number theory. He is an elected fellow, Singapore Natl. Acad. of Science, and Inst. of Mathematical Statistics; elected member, International Statistical Institute. He has served as Associate Editor of the journals Bernoulli and Statistica Sinica.