Thirteen bread wheat ( Triticum aestivum check for this species in other resources L.) cultivars popular in the highlands of Ethiopia and representative of the period from 1949 to 1987 were studied for two cropping seasons in Ethiopia to estimate progress made in improving grain yield. The selected cultivars were grown with the effects of other genetic changes minimized by using fungicides to control foliar diseases, nets to prevent lodging, and periodic hand weeding to control weeds. Adequate levels of nutrients were also supplied. Significant differences were observed among cultivars for all crop parameters studied. The grain yield of bread wheat cultivars released since 1949 has increased at a mean rate of 77 kg ha-1yr-1 (2.21%) as measured in central Ethiopia and 50 Kg ha-1y-1(1.77%) under warmer and drier conditions in southeastern Ethiopia. Grain Yield was significantly and positively correlated with harvest index, grains m-2, spikelets spike-1 and grains spike-1. Genetic improvement has substantially increased the grain yield of rainfed bread wheat in the highlands of Ethiopia, resulting from an improved harvest index associated with an increased number of grains spike-1 and, as a result, grains m-2. Wheat breeders in Ethiopia should continue to emphasize spike fertility as a selection criterion for high grain yield.