Precipitating polyclonal rabbit antiserum to monkey immunoglobulins, IgG, IgA and IgM, heavy and light chains. In precipitating techniques as immunoelectrophoresis, single and double radial immuno- diffusion (Mancini, Ouchterlony) to identify and measure immunoglobulins; as secondary antibody to precipitate immunoglobulins in normal monkey serum. This antiserum is not intended for use in non-precipitating antibody-binding or other highly sensitive assays. For such uses labelled and unlabelled cytochemical and immunoassay grade reagents meeting the necessary additional specificity and performance requirements are available.