Immunoglobulins (Ig) are critical components of the immune system and play a major role in eliciting immune response against pathogens. Five heavy-chain isotypes (IgA, IgD, IgE, IgG, and IgM) mediate specific biological functions, including responses to pathogens and immunological diseases such as allergy and autoimmune disorders. IgG, a monomer, is the dominant immunoglobulin class present in serum. There are four subclasses of IgG, namely IgG1, IgG2, IgG3, and IgG4. IgG is commonly used as a diagnostic tool for humoral immunodeficiencies, autoimmune diseases, liver diseases, chronic inflammatory diseases, haematological disorders, infections, and lymphoid malignancies. This kit provides the assay-specific components for the quantitative determination of IgG in human, cynomolgus monkey, and rhesus monkey samples.