Subadult striped bass, Morone saxatilis, tagged with temperature-sensing ultrasonic transmitters in April-October and monitored in freshwater lakes generally occupied waters of 20–24 C, when these temperatures were available. When they were not (spring and fall), fish occupied nearly the warmest water available at depths > 1.5 m. Excursions of less than 2 minutes duration to warmer and to cooler water than was generally occupied were common in spring and summer. A thermal niche for subadult striped bass of 20–24 C centering near 22 C, as suggested by these results, would have important implications for managing this species in fresh water.