Morlcandia arvensis (L.) DC. has been identified as a C3-C4 intermediate species based on its low CO2 compensation point, low photorespiratory activity and partial degree of Kranz anatomy. However, M. arvensis does not have key enzymes for C4 photosynthesis such as phosphoenolpyruvate carboxylase (PEPC). We introduced maize C4 PEPC cDNA under the control of the cauliflower mosaic virus 35S promoter into M. arvensis by Agrobacterium - mediated gene transfer. Most of the transgenic plants accumulated large amounts of the transcripts of the introduced PEPC gene, although the amount of the PEPC protein was rather small. The amounts of the maize PEPC protein in the transgenic plants were positively correlated with the activity of PEPC. Elevated PEPC activity, twice as high as that of the wild-type control, was observed in some transgenic plants.