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The effects of grazing intensity on cattle performance, profitability and the sustainability of forage production have been monitored on mixed-grass season-long pastures at the NDSU - Central Grasslands Research Extension Center northwest of Streeter since 1989. Three replicates of five treatments were included: no grazing, light, moderate, heavy and extreme grazing. Our goal was to stock the pastures each year so when the cattle were removed in the fall, 65, 50, 35 and 20 percent of the forage produced in an average year remained on the light, moderate, heavy and extreme treatments, respectively. Average daily gain and body condition score decreased with increasing grazing intensity. This effect was significant (P?0.05) in most but not all years. Regression of gain/ton (total weight gain of all animals/ton of available forage) and stocking rate showed that gain initially increases with stocking rate, but then decreases at higher stocking rates.Regression analysis shows that the constant stocking rate with the greatest average gain/ton of forage from 1991 to 2014 was 2.57 animal unit months (AUMs)/ton of forage, and the average gain/ton would have been 78.8 pounds/ton. If cattle prices were constant from spring to fall, then return/ton (dollars returned to the enterprise/ton of forage) would peak at a stocking rate somewhere below maximum gain/ton, with the exact point depending on carrying costs. The stocking rate with the maximum return/ton during the last 24 years would have been 2.53 AUMs/ton, with an average annual return of $54.01/ton. Although the most profit would have been made at 2.53 AUM/ton, forage production would be reduced and plant species composition would be altered. Based on vegetation response to stocking rates, the best compromise between profitability and sustainability appears to fall between a moderate stocking rate (0.69 AUM/ton) and a heavy stocking rate (1.32 AUM/ton).