Lima bean yields are lower in Delaware than in other lima-bean-producing states. One of the factors that contributes to the low production is the high temperatures that occur during production. Six commercial varieties of lima beans, both fordhook and baby lima bean types, were grown in a glass greenhouse at either 25C or 35C daytime temperatures to screen for heat tolerance. Plants grown at high temperature were typically shorter and more bushy than plants grown at 25C. Few, if any, buds, flowers, or early pods remained on plants at harvest if the plants were grown at 25C, while plants grown at 35C were still producing buds and flowers. Lima bean yields were generally reduced at 35C. The magnitude of the effect on yield ranged from `F1072', which had a 100-fold decrease in yield, to `Early Thorogreen', which demonstrated a slight increase in yield in response to increased temperatures.