The CO2 compensation point and its relation to the chloroplast DNA (cpDNA) type were investigated on the somatic hybrids between Brassica oleracea, a C3 plant and Moricandia arvensis, a C3-C4 intermediate plant. The fragment patterns of cpDNA digested with restriction endonuclease (Xhol) showed that the somatic hybrid plants had the cpDNA of either B. oleracea or M. arvensis. Out of 11 plants investigated, 5 plants had the cpDNA of B. oleracea, while 6 had that of M. arvensis. However, both types of the hybrids showed as high a CO2 compensation point as B. oleracea irrespective of their cpDNA. In this respect, the C3-C4 intermediate character of M. arvensis was not expressed in the hybrids.