Objective Suicides among active duty US Army personnel have been increasing since 2004, surpassing comparable civilian rates in 2008. This analysis uses US military data to assess suicide rates for the 2-year period 2007–8, and examines relative risks (RR) of suicide associated with mental health disorders. Methods Historical trends of US Army suicides were assessed using 1977–2008 data from Army G-1 (Personnel). Suicide rates, RR and the 2000–8 trends of mental health disorders were calculated using data from the Defense Casualty Information Processing System and Defense Medical Surveillance System. Results A total of 255 soldiers committed suicide in 2007–8 (2008 rate 20.2 per 100 000). Factors associated with higher suicide risk included male gender, lower enlisted rank and mental health disorders treated on an outpatient basis (RR 3.9), as well as a number of mental health disorders (mood disorders, anxiety disorders, post-traumatic stress disorder, personality/psychotic disorders, substance-related disorders and adjustment disorder; RR range 4.7–24.5). Analysis of historical trends suggested that 25–50% of the suicides that occurred in 2008 might have been related to the major commitment of troops to combat beginning in 2003. Conclusions The recent increase in suicides parallels an increase in the prevalence of mental disorders across the army. This finding suggests that increasing rates of clinically treated psychopathology are associated with increasing rates of suicides; these rates probably serve as sentinels for suicide risk in this population. Soldiers seeking treatment for mental disorders and substance abuse should be a focus for suicide prevention.