BACKGROUND Identifying characteristics that influence smoking behavior among military personnel is critical to protect health and operational functioning. PURPOSE This study prospectively examined rates of cigarette smoking and predictors of changes in smoking behavior as a function of Iraq deployment. METHODS One thousand eighty-two US Army soldiers (n = 773 Iraq-deployed; n = 309 nondeployed) completed assessments at two sessions [time 1: April 2003-July 2004; time 2: May 2004-July 2004 (nondeployers); January 2005-September 2006 (deployers)]. RESULTS Approximately 48 % of participants smoked at both time points, with 6 % initiating smoking and 6 % quitting. Smoking initiation was associated with warzone stress exposure; female gender and high military unit support predicted cessation. Military rank and alcohol use were associated with both smoking initiation and cessation. CONCLUSION Findings highlight the potential benefits of targeting risk factors for cigarette smoking in comprehensive military health programs aimed at smoking prevention and cessation.