An experiment was conducted using male Cobb x Cobb broiler chicks to evaluate the effect of two oxygen levels on the incidence of ascites, performance, and blood chemistry. Ascites occurred in the 13.6% oxygen groups on the fifth day of the experiment. Body weights and survivability were significantly lower (P < 0.05) in chicks maintained at the low oxygen level than in controls (20.6% oxygen). Hematocrits were significantly higher only in chicks with ascites at the 13.6% oxygen level. Hemoglobin was significantly higher (P < 0.05) in chicks with ascites at 13.6% oxygen than in chickens at 20.6% oxygen. Lactate dehydrogenase values were significantly higher in non-ascitic chicks maintained at 13.6% oxygen and in chicks with ascites at 20.6% oxygen than in non-ascitic chicks 20.6% oxygen.