We use the Semliki Forest Virus (SFV) as a tool for protein expression in primary cultures of rat hippocampal neurons. These cells develop in vitro into polarized neurons that can be infected with recombinant SFV with an efficiency of 60 - 80%. SFV-driven protein expression is detectable within 3-4 hours postinfection, at which time the newly-synthesized proteins are mainly present in the cell soma. By 6 to 8 hours postinfection foreign proteins are detectable in the neurites. Protein expression can continue for up to 48 hours. However, after 8 - 10 hours infected neurons start to suffer from cytopathic effects as evidenced by a change in morphology and detachment from the coverslip. The infection does not seem to affect the polarized distribution of proteins. Upon overexpression of rab8, a somatodendritic distribution is observed, similar to that of the endogenous protein. Therefore, the SFV expression system is suitable for short-term expression of proteins and can be used successfully to study the polarized distribution of heterologous proteins expressed in cultured hippocampal neurons.