With the intention of evaluating an avidine-peroxidase biotinilated technique, the antirabies' sera, produced in the INS, was used for the detection of the rabies' virus in mouse brain tissue, treated with various types of fixers and various antisera dilutions. The experimentally infected animals were killed by intra-aortic perfusion with various fixers; their brains were recovered, cut into 60 pm slices and submitted to immunodetection. It was found that the normally used fluorescent dilutions presented strong non-specific marking without improving detection. In this work a protocol which is fast and easy is presented, which could be useful for the observation of suspect samples.