Growth rates of juvenile painted turtles (Chrysemys picta) in Algonquin Park, Ontario, were positively correlated with summer air temperatures. To test whether this correlation was caused by temperature, or indirectly caused by increased food availability, I provided hatchling painted turtles with varying opportunities to thermoregulate, and either fed these animals to satiety, or they ate about 60% of this amount. Growth was positively correlated with temperature, but not with quantity of food. Passage rate of food was faster in turtles which were allowed to bask, which may have increased the amount of food warm turtles could consume, therefore leading to faster growth of warm animals. However, turtles showed few behavioural or metabolic responses to temperature which might optimize growth rates. One behavioural change that was observed was reduced activity in turtles that were prevented from basking.