The objective of this study was to compare the effectiveness of euthanasia gases administered to 2 age groups of piglets: neonates (less than 3 days, n=160, BW 2.61 ± 0.81 kg) and weaned (16 to 24 days, n=160, BW 4.62 ± 0.76 kg). Two different gases were explored in this study: 100% CO2 and a 50:50 CO2:Argon (CA) gas mixture. Each gas was administered at 3 flow rates: 35%, 50% and Prefill + 20%, chamber volume exchange rate per minute. Latencies, durations and occurrence of behavior and physiologic changes were observed using direct observationand video. Neonate piglets were euthanized as quickly as or faster than weaned piglets for all gases and flow rates. For the neonate relative to the weaned piglet, average loss of posture over all gas treatments was 99 vs. 142 (seconds) and last movement was 360 vs. 392 (seconds). Neonates also displayed fewer incidences and shorter durations of behavioral indicators of distress and sensation relative to the weaned piglets. Thus concerns for gas euthanasia, when applied appropriately, are not greater for the neonate relative to the weaned piglet. Additionally, procedures developed to euthanize weaned piglets will likely be successful when applied for the neonate, but not viceversa.