Recombinant adeno-associated viral vectors (AAVs) are very promising gene transfer tools for the nervous system. We have compared the efficiency of gene expression of seven AAV serotypes in young adult rats following a single injection in a major nucleus of the mid brain, the red nucleus, which is the origin of the rubrospinal tract. AAV serotypes 1-6 and 8 and a lentiviral vector (LV) were used, all encoding green fluorescent protein (GFP) under control of the cytomegalovirus (CMV) promoter. AAV vectors were titer matched at 5x10(11) genomic copies (GC)/ml and 1mul was injected into the red nucleus. The proportion of transduced neurons in the red nucleus was determined at 1 and 4 weeks post-injection. AAV1 would be the vector of choice if the aim would be to overexpress a transgene at high level for a longer period of time. AAV5 and AAV8 would be the preferred serotype if onset of expression is should be somewhat delayed. The use of lentiviral vectors should be considered when transduction of both glial cells and neurons is required. Serotypes 3 and 4 did not transduce red nucleus neurons. AAV1, AAV6 and LV would be the vectors of choice if the aim of the experiment would be to rapidly express a transgene. The current data are important for the design of experiments that aim to study the effects of transgene products on the regenerative capacity of injured red nucleus neurons.