Environmental conditions to which amphibians are exposed can influence embryonic development and physiology and thus alter later life-history traits. We exposed Ambystoma maculatum eggs to oxygen partial pressures (PO₂) of 1.6, 3.5, 7.9, 12.4, and 18.1 kPa. No eggs survived in the 1.6-kPa treatment, but 94% of the eggs incubated at greater PO₂s survived to hatching. We reared the resulting larvae individually in the laboratory until metamorphosis. Larvae from the 3.5-kPa treatment had reduced posthatching survival. Exposure to hypoxia while in the egg resulted in slowed growth early in the larval period. As a consequence, larvae from the 3.5-kPa treatment averaged 11 d longer to reach metamorphosis than larvae from the 18.1-kPa treatment. Additionally, larvae from an intermediate level of hypoxia (7.9 kPa) were larger at metamorphosis than larvae from eggs reared at either greater or lesser PO₂s. Overall, our results indicate that environmental conditions to which eggs are exposed have the potential to alter future development and survival, even if the effects appear relatively minor at the time of hatching. They also point toward the need for further studies to understand the developmental and physiological mechanisms behind these effects.