A practical in situ hybridization (ISH) method has been developed for the rapid diagnosis of pseudorabies virus (PRV) infection in pigs. The method utilizes routine formalin fixed and paraffin-embedded tissue sections, non radioactive biotin-labelling, simple hybridization procedure and diaminobenzidine (DAB) silver enhancement detection system. The rapid (ISH) method showed concordance with the direct filter hybridization (DFH) and with the peroxidase-antiperoxidase (PAP) assays. By the simplified ISH, diagnosis can be made within two days.