This study was planned to help the diagnosis of borderline leprosy by application of the in situ PCR. In situ PCR was performed in the tissue from skin biopsy using the Dig DNA probe synthesis kit®(Behringer Mannheim Co) on silanized slides and Dig incorporated PCR products were visualized by alkaline phosphatase conjugated anti-Dig antibody using NBT/BCIP as substrate. In the borderline lepromatous patients homogeneous or granular strong deposits were observed mainly within the cytoplasm of the histiocytes and proliferated Schwann cells. Some secretory cells of sweat glands, erector pile muscle and a few endothelial cells were weakly stained. In the tuberculoid leprosy patients no positive signal was observed. In conclusion in situ PCR can be applied on the tissue of berderline lepromatous patients of which sample does not need proteinase K treatment.