Localization of Plum pox virus (PPV) in stem and petiole tissues of four susceptible and four resistant apricot cultivars has been studied. Consecutive 1-mm spaced transverse sections were taken from the tissues and were printed onto nitrocellulose membrane in duplicate. For virus-specific detection, one series of prints was probed with an antibody to PPV coat and the density of stains was evaluated by light microscopy. Another series of prints was treated with a substrate but not with the antibody to reveal non-specific staining due to endogenous peroxidases. The virus was currently detected in all inoculated susceptible cultivars but only in one inoculated resistant cultivar (Harcot). In the stem tissues, the virus was localized in the pith and in the xylem. In the petiole tissues, it was localized in the epidermis and in cortical and medullae parenchyma. Non-specific staining was observed only in the stem sclerenchyma and in the petiole phloem.