Transient gene expression was studied in isolated protoplasts of barley (Hordeum vulgare L. cv Himalaya) transformed by electroporation. Two plasmid constructions were used, both of which contained the gene coding for neomycin phosphotransferase II (nptII) as a reporter gene. In one plasmid the reporter gene was under the control of an α-amylase group 1 gene promoter of barley and in the other, used as a control, under the CaMV 35S transcript promoter. Protoplasts were isolated from three different types of tissue: the aleurone layer, the scutellar epithelium and the mesophyll. All three types of protoplasts electroporated with 35S -nptII plasmid construction showed strong NPTII activity on which GA3 and ABA had no effect. In protoplasts isolated from the aleurone layer and scutellum the expression of amy-nptII was low when compared with the expression of 35S -nptII. In aleurone protoplasts GA3 enhanced the expression of amy-nptII about tenfold and ABA prevented the action of GA3. In protoplasts isolated from the scutellar epithelium GA3 did not affect the low level of expression of amy-nptII. In mesophyll protoplasts the amy-nptII was not expressed at all.