The aim of this work was to study the role of ADPglucose pyrophosphorylase (AGPase) in starch biosynthesis of non-photosynthetic organs. Agrobacterium tumefaciens was used to transform potato plants (Solanum tuberosum L. cv. Desireé) with the wheat AGPase genes (AGP-S and AGP-L, coding for the small and large subunits, respectively). Neither of these genes contains a recognisable plastid targeting sequence. Southern analysis and analysis of starch content identified four lines that contained both wheat sequences. Immunoblotting indicated that, in the tubers, three lines expressed the wheat small subunit (AGP-S), but AGP-L cross-reacting protein was not apparent. The fourth transgenic line had reduced AGPase activity. AGPase activity in the AGP-transgenic tubers ranged from 15 to 165% of that found in β-glucuronidase (GUS) control lines.