In an experiment with new hexaploid wheat lines existing lines and other tetraploids was conducted in the Rabi (post-rainy) 2001 and 2002 dry seasons. The data on yield and yield components shows that the tetraploids had more spikes plant-1 but fewer seeds spike-1 and a lower seed weight spike-1. The most important yield component the 1000-grain yield was shown by the hexaploids. The new hexaploid lines DL-1266-1 and DL-1266-2 had the maximum grain growth rate at 5 – 15 days after anthesis (DAA). Line DL-1266-2 had the highest grain growth rate 0.09 g g-1 day-1. Photosynthetic rate values showed that the hexaploids had a higher rate than the tetraploids. Generally, at 7 and 15 DAA, the photosynthetic rate was higher compared to 25 DAA and 35 DAA. It appears that in the high yielding hexaploids (DL-1266-1 & DL-1266-2) a better photosynthetic rate and better mobilization of photosynthates during grain filling contributes to their higher yield.