This research is part of a long-term study on the life-history of the painted turtle ('Chrysemys picta') that was initiated in Algonquin Park in 1978. I used long-term data to test the hypothesis that widely documented annual variations in egg mass (EM) and egg length (EL) are inversely related to the temperature of the spring or fall periods of follicular development. I also tested the hypothesis that clutch frequency (CF - the number of clutches per year) and clutch size (CS) are positively related to the temperatures of the previous fall. CF was related to temperature in smaller, but not in larger females. Mean EM, EL, CS and (accordingly) the mass of the first clutch were inversely related to the temperature experienced just prior to nesting season onset. I show that this inverse relationship is likely an artifact of selection for a temperature-moderated gonadal cycle, and I argue that the Smith-Fretwell model of egg size optimization is applicable to 'C. picta' in the Algonquin population.