Synthetic human calcitonin monomeric (hCT(m)) and tetrameric (hCT(t)) genes were cloned under the control of the 35S cauliflower mosaic virus (CaMV) promoter linked to the 5'-non-translated leader sequence of tobacco etch virus (TEV). The resulting constructs were cloned into the binary vector Bin19 and potato minituber discs were transformed using an Agrobacterium strain. Northern dot-blot and RT-PCR were applied for monitoring of transcription. Translation of the hCT(m) and hCT(t) mRNAs was studied by radioimmunoassay and molecular size of the recombinant proteins was determined by SDS-PAGE. The estimated average yield of recombinant hCT in the transgenic potato plants was about 0.02% of the total soluble protein.