We examined the temporal profile of the expression of brain-derived neurotrophic factor (BDNF) cDNA containing a viral promotor following the injection of liposome cDNA complexes into the intact and traumatically injured rat brain. In situ hybridization and PCR confirmed the presence of injected BDNF cDNA for at least 6 days after injection. A similar profile of BDNF cDNA was observed when it was injected following cortical impact injury. mRNA was also localized around the injection areas. These results suggest that liposome-mediated delivery of neurotrophin cDNA may be a practical gene transfer method for treating traumatic brain injury.