Cotyledonary somatic embryos of white spruce (Picea glauca (Moench) Voss) were subjected to microprojectile bombardment with a gene construct containing a gus::nptII fusion gene. Somatic embryos were used to re-induce the embryogenic tissue after bombardments. Histochemical assay using X-gluc as a substrate showed that all the embryos (100%) were GUS positive 48 h after bombardment. However, only thirteen out of 605 embryos (2.2%) remained GUS positive after two months in culture. Three of those thirteen (23%) embryo-derived tissues consistently showed GUS activity for eight months in culture. These putatively transformed embryogenic tissues were subjected to Southern blot analysis and the results suggested integration of the gus::nptII gene expression cassette in the white spruce genome.