Environmental effects on blood characteristics of macaques were examined by comparing several blood indices of the free-ranging crab-eating monkeys (Macaca fascicularis) in two distinct regions of Bali Island, Indonesia. The total plasma protein level and concentrations of creatinine and sodium ion were higher with macaques of Teluk Terima in the west part of Bali Island (dry area) than those in the central Bali (wet area). Results indicated that water deficiency in the dry area significantly affects the blood characteristics of macaques.