When repeatly injected to Fisher Inbred rats, boiled Walker tumour extracts induced non specific and specific reactions; non specific reactions being catabolism, thymus involution, adrenal hypertrophy and perturbation of serum proteins relative distribution. The specific reactions attributable to the presence of the specific tumoral antigen in the tumour extracts are immunoallergic arthritis, liver and spleen hypertrophy, acceleration of serum albumin electrophoretic migratory rate and the apparition of the specific antigen in the liver.