Immature turtles were trained to depress a lever to secure access to air while submerged in water. Rate of responding was inversely related to duration of exposure to air following each response. Periodic extinction produced a decline in rate during extinction and compensatory increases during continuous reinforcement. S''s responded less for air containing 10% carbon dioxide. Rate of responding increased when S''s diets were augmented with uncooked meat, and there was an increase by a factor of approximately 2 in the rate of lever pressing with a 10[degree]C rise in temperature. This latter phenomenon may be mediated by direct effects of temperature on external respiration, but is probably not related to change in uptake of oxygen from the water immersing Ss.