Using horseradish peroxidase (HRP)-conjugated lectins for pre-embedding labelling we have shown differences in ultrastructural localization of saccharides in cell compartments of fowl plague (FP) virus-infected and uninfected MDCK cells. Lectinochemical staining of the cell compartments in the case of FP virus-infected MDCK cells was less intensive as compared with uninfected cells. Also certain differences in the staining of subcompartments of cell organells were seen. Staining of uninfected cells with Pisum sativum agglutinin (PSA)-HRP revealed an extensive visualization of Golgi complex, mainly its cis-part, TGN vesicles and lysosomes. Staining of FP virus-infected cells with the same lectin marked very lightly rough endoplasmic reticulum and not at all the Golgi complex. Staining with Erythrina cristagalli agglutinin (ECA)-HRP revealed a picture very similar to PSA-HRP staining of uninfected and FP virus-infected cells. The differences in the lectinochemical staining of cell organelles of FP virus-infected and uninfected cells may be connected with the inhibition of cell protein synthesis during FP virus morphogenesis.