Offspring phenotype can be affected by maternal effects, developmental conditions, and clutch identity. We examined the contribution of maternal effects, egg incubation temperature, and clutch identity to variation in hatching success and hatchling body size of the snapping turtle, Chelydra serpentina. We collected 726 eggs representing 24 clutches from the John Heinz National Wildlife Refuge in 1997. We examined a subset of eggs (78) for water and solid content and incubated the remaining eggs. Wet shell and wet nonshell made up 10.96% and 88.05% of the total egg mass, respectively, and dry solids, dry shell, and total water accounted for 22.78%, 7.14%, and 70.07% of total egg mass. Both mass of total water and solids in the nonshell fraction increased with egg size, although solids accounted for slightly less proportional mass in large eggs than in small eggs. Egg mass was correlated with mass at hatching, but explained only 47% of the variation in mass at hatching. Both clutch identity and egg incubation temperature affected hatching success and hatchling size. Although maternal effects no doubt play an important role in determining hatchling size, other factors, independent of maternal effects, influenced hatchling size.