On January 6, 2005, two freight trains collided in Graniteville, South Carolina (approximately 10 miles northeast of Augusta, Georgia), releasing an estimated 11,500 gallons of chlorine gas, which caused nine deaths and sent at least 529 persons seeking medical treatment for possible chlorine exposure. The incident prompted the Agency for Toxic Substances and Disease Registry (ATSDR) to review data from its Hazardous Substances Emergency Events Surveillance (HSEES) system and update an analysis of 1993-1998 railroad events. The HSEES system is used to collect and analyze data concerning the public health consequences (e.g., morbidity, mortality, and evacuations) associated with hazardous-substance--release events that occur in facilities or during transportation. This report describes the event in South Carolina, which is not part of the HSEES system, and two others from HSEES, and summarizes all rail events reported to HSEES from 16 state health departments during 1999-2004. Local government agencies, employers, and first responders can help reduce morbidity and mortality from transit-associated hazardous-substance releases by examining historical spill data for planning purposes, developing emergency response plans, undergoing proper hazardous materials (HazMat) training, and reviewing epidemiologic investigation data.