The environmental vibrations, caused mainly due to train-road traffic, construction activities and factory operations, are being investigated, globally, for their prediction,monitoring, mitigation and evaluation, basically, to improve the quality of life and robust infrastructure in the modem high tech society. The School of Civil Engineering, Beijing Jiaotong University in China is honored tobe the organizer of the 4th International Symposium on Environmental Vibrations:Prediction, Monitoring, mitigation and Evaluation （ISEV2009）. This symposium,sequel to the first one held in Hangzhou, China in October 2003, the second one in Okayama, Japan in September 2005, and the third one in Taipei in November 2007,provides an intemational forum to exchange the knowledge, ideas and experiences for pursuing research on prediction, control and mitigation of environmental vibrations.This series of meetings on environmental vibrations were made possible due to the continuous efforts of four professors: Prof. Yih-Hsing Pao, Honorary Chairman of the symposium, who belongs both to the National Taiwan University and Zhejiang University, Prof. Hirokazu Takeyima of Okayama University, Prof. Yunmin Chen of Zhe jiang University, and Prof. Yeong-Bin Yang of the National Taiwan University.