Cober, E. R. and Voldeng, H. D. 2012. A retrospective look at short-season soybean cultivar development in Ontario. Can. J. Plant Sci. 92: 1239-1243. Canadian soybean production has increased from about 63 000 ha in 1951 to 1.2 million ha in 2006 with expansion from southern Ontario to shorter season areas. From 1971 to 2000, soybean production in Ontario increased sixfold. Using annual reports from 1971 to 2000 of short-season trials in Ontario, we found that the number of reported cultivars remained between three and five until 1984 when the number of cultivars started to increase at the rate of about 2.5 yr^-1. The amount of time that cultivars remained in the reports has declined from 12 to 4 yr on average over the 30-yr period. Long-lived cultivars, however, were developed throughout the period including: Hardome, Merit, Evans, Maple Arrow, Bicentennial, Maple Glen, KG 41, OAC Eclipse, 9071, OAC Bayfield, PS 36, and S03-W4. Over the 30-yr period of cultivar testing, short-season seed yield increased about 600 kg ha^-1, while mean time to maturity decreased about 10 d. During the same time, mean Ontario commercial seed yields increased about 750 kg ha^-1. Over the 30-yr period, the number of short-season cultivars in annual reports increased 36-fold, while provincial yield increased only 1.4-fold. If the number of cultivars in annual reports is an indication of breeding effort, large research investments may be necessary to increase future yield improvement.