This work is part of the overall development of the BEAM code and we thank our collaborators, Drs Charlie Ma and Bruce Faddegon at NRC and Rock Mackie at University of Wisconsin for their work to make this code work so well. We wish to thank following individuals for providing the data related to various accelerator beams: Dr. Carl Ross for data related to the NRC accelerator, Carol Wells and Rock Mackie of the University of Wisconsin for data related to the Clinac 2100C, Cal Huntzinger of Varian for supplying detailed information on the Clinac 2100, Dr. Joanna Cygler of Ottawa Regional Cancer Center for data related to the KD2 and the Therac 20, Mr. Mark McCarthy of Siemens for supplying information on the KD2, Drs. Jack Janssen and Henk Huizenga of the Dr Daniel den Hoed Cancer Clinic for data related to the Siemens KD2, and Dr. Chen Chui of Memorial Sloan-Kettering Cancer Center in New York for the data related to the Racetrack Microtron. We thank Dr. Alex Bielajew for supporting the EGS4 system at NRC and his help running EGS_Windows and Dr Michel Proulx for work on the computing systems. Thanks also to Andrew Booth at NRC who helped set up the digital data files for access on the WWW. This work is partially supported by NCI grant R01CA52692. George Ding is the recipient of the MRC Studentships Award and is grateful to the Medical Research Council of Canada.