New England Journal of Medicine (Internet / Print) 01/12/06 A biosafety level 4 laboratory is a box within a box — a sealed environment within a larger building (see diagram), buttressed by strict security measures. Since mid-2004, one such laboratory, 2000 ft2 in size, has operated in the middle of a medical school campus, at the University of Texas Medical Branch (UTMB) in Galveston (see photo). Led by David Walker, chair of the pathology department, planning for the facility began at UTMB in the 1990s — years before the attacks on September 11, 2001, and before emerging infectious diseases and bioterrorism became widespread concerns. Walker explained the rationale to me when I visited the university; it is to allow deadly pathogens to be studied with the same rigor as are other organisms.