Immunoglobulin G (IgG) is the most abundant immunoglobulin in serum and is predominately involved in the secondary immune response. The IgG subclasses are designated 1, 2, 3 and 4 based on their relative prevalence in serum. The sensitive quantitative measurement of total cynomolgus macaque (Macaca fascicularis) monkey IgG antigen in serum, plasma, hybridoma cell supernatants, ascites or other biological fluid samples is easily performed with this 96 well strip format ELISA kit. The assay does not distinguish IgG subclasses. The kit does not cross react significantly with human, mouse, rat, dog, sheep, pig or rabbit IgG. The concentration of IgG in normal cyno monkey serum ranges from 5 to 12 mg/ml. The assay measures cyno monkey IgG in the 0.1-100 ng/ml range. Samples giving cyno monkey IgG levels above 100 ng/ml should be diluted in blocking buffer before use. A 1:1,000,000 to 1:10,000,000 dilution for serum is suggested for best results. Cyno monkey IgG will bind to the monoclonal capture antibody coated on the microtiter plate. After appropriate washing steps, biotin labeled monoclonal anti-cyno IgG primary antibody binds to the captured protein. Excess primary antibody is washed away and bound antibody is reacted with horseradish peroxidase conjugated streptavidin. Following an additional washing step, TMB substrate is used for color development at 450nm. Color development is proportional to the concentration of cyno monkey IgG in the samples. A standard calibration curve is prepared in blocking buffer using dilutions of purified cyno monkey IgG and is measured along with the test samples. All reagents and standards are provided in these ELISA kits.