Energy allocation to eggs and nest site selection by females can affect life-history variables such as offspring size, offspring number, developmental rate, survivorship, growth rate, and performance in oviparous reptiles. Nest site selection can affect offspring phenotype by altering incubation conditions. I present evidence of a positive effect of female size on clutch size, egg mass, and nest depth through the study of trackways left by female river turtles, Podocnemis expansa, on their nesting beaches. Larger females laid larger clutches composed of larger eggs, which were buried deeper than clutches laid by smaller females. The data suggest that P expansa does not conform to optimal propagule size models. Neither egg size nor clutch size reached a plateau as female size increased. Females seem to allocate the extra energy (in absolute terms) gained allometrically with increasing size and age to both number and size of eggs. There was no evidence of a trade-off between egg size and number after removing the effect of female size. Larger eggs produced larger hatchlings that survived better but grew less than individuals of smaller initial size during the first two months of life, under unlimited food conditions. I suggest that fitness of female P expansa increases by producing larger eggs because of the advantage that larger hatchlings have in survival. Deeper nests experience cooler temperatures and tend to produce a higher percentage of males than more superficial nests. Therefore, there is a potential for important effects of nest depth on sex ratios produced by different sized females within the population and possibly by single females throughout their lifetime. Constant temperature in artificial incubation experiments had an effect on the size of individuals at hatching, but differences vanished by the second month of age via the greater growth rate shown by individuals of smaller initial size.