Background The use of decompressive craniectomy (DC) as an aggressive therapy for traumatic brain injury (TBI) has gained renewed interest. While age and the Glasgow Coma Scale (GCS) are frequently correlated with outcome in TBI, their prognostic values after decompressive cra-niectomy are ill-defined. Methods We retrospectively reviewed data from 103 TBI patients treated with DC from 2001 to 2003. Age, preoper-ative GCS, and injury severity scores were recorded. Outcome at time of discharge was measured with the Glasgow Outcome Scale (GOS). Patients were stratified into the following age groups: <35, 35-49, 50-64, and ≥65 years. Spearman's correlation coefficients between age, GCS, and GOS were calculated for the entire population and each age group. Findings Mortality rates for each age group were 19.2%, 66.7%, 60%, and 80%, respectively. There was a significant negative correlation between age and GOS (r=-0.42, p< 0.0001) and patients <35 years had significantly better outcomes than patients ≥35 years (p<0.0001). The overall correlation between GCS and GOS did not reach significance (r=0.18, p=0.076). When stratified by age, there was a significant correlation between GCS and GOS only in patients 35-49 years (r=0.51, p=0.011). Conclusions This data suggests that in TBI patients treated with DC, age correlates with outcome while the correlation between GCS and outcome is age-dependent.