Abstract: Illegal drug use may be a consequence of sustaining a serious physical combat injury, though no known research has investigated this in a UK setting. This analysis utilises the baseline data from a longitudinal cohort (ADVANCE), to assess whether 577 UK military personnel who sustained serious physical combat injuries reported more illegal drug use compared to 565 frequency-matched personnel without such injuries. Most personnel reported no illegal drug use in the past year (88.7%). Cocaine was the most common drug reported in the past year, followed by cannabis. Injured personnel had greater odds of reporting illegal drug use in the past year compared to the comparison group (injured group: 16.3%, comparison group: 5.4%; Odds Ratio (OR) 3.09 (95% CI 2.03, 5.31)), however, no differences were observed amongst veterans in each group (OR 0.67 (95% CI 0.40, 1.27)). Higher prevalence of illegal drug use was observed amongst those of white ethnic background, lower rank, those who were single, younger, veterans, and those who reported a probable mental illness, suicidal ideation or heavy alcohol use/tobacco use. Veterans who left service at a younger age and with a shorter length of service were also identified as having higher prevalence of illegal drug use. UK Armed Forces personnel who sustained serious physical combat injuries in Afghanistan report more illegal drug use in the past year compared to demographically similar personnel without serious physical injury. Greater prevalence of illegal drug use was evident in those that left service, with >20 % of veterans reporting illegal drug use in the past year.