Immunoglobulins (Ig) in feline sera and secretions were identified by immuno-electrophoresis and immunodiffusion with rabbit antisera prepared to feline IgG, IgA, IgM, and whole serum. Adult cat sera, colostral whey, postcolostral sera, tears, and nasal secretions contained IgG, IgA, and IgM. IgG was the only Ig identified in precolostral sera and cerebrospinal fluid. Milk, intestinal contents, pooled allantoic and amniotic fluids, and saliva from adult cats and urine from suckling kittens contained IgG and IgA. Ig were not detected in urine from adult cats. Bile was unique in that IgA and IgM were the predominant Ig.