||In the process of genetic improvement of bread wheat, photosynthetic rate per unit leaf area has decreased significantly from the maximum photosynthetic rate (Pmax) of the crop's diploid ancestors (donors of the A, B, and D genomes that make up hexaploid bread wheat). Much of the grain yield improvement of bread wheat accomplished by breeders can be traced to a change in the partitioning of assimilate to the grain, i.e., an increase in harvest index. It is the perception of wheat scientists that this avenue of grain yield improvement has pretty much run its course. However, it may be possible to increase harvest index (and subsequently grain yield) by increasing total biomass. This Wheat Special Report presents the first efforts at CIMMYT to alter wheat biomass by increasing Pmax. It seems there is potential for using synthetic hexaploids, developed by our wide crosses laboratory, as a "bridge" to transfer the higher photosynthetic rate found in the diploid ancestor, Triticum tauschii, to bread wheat. The results are not definitive, but they are encouraging and certainly point to exploring this route further. The chlorophyll alb ratio is discussed as a potential screening tool for Pmax.