Checking the internal temperature of the breast and thigh is the best way to know when whole poultry is done, so using an accurate thermometer is crucial. A leave-in thermometer (top) stays in throughout the roasting time and allows you to check the temperature without opening the oven door. An instant-read thermometer (middle and bottom) is inserted near the end of roasting time. These thermometers are interchangeable; choose the one that best suits your needs. A minimum temperature of 160°F will destroy bacteria, but the breast and thigh have different temperatures for ideal doneness.