Normal cynomolgus serum (NCYS) is tested for complement activity and certified to possess fully functional classical and alternative pathways of activation. NCYS was prepared from mixed gender cynomolgus monkeys. Each sample of blood was collected without anticoagulants and, after coagulation, the liquid portion was separated by centrifugation. NCYS was filtered through a 0.22 µm filter, aliquoted and frozen at -80o C. All testing for complement activity was performed on the subsequently thawed samples to guarantee that the functional activity reported is what customers will receive when the samples are thawed. Complement activity is stable for several years if NCYS is stored at -70o C or below continuously. A slight degradation of activity may be observed following additional freeze thaw cycles.