A majority of guinea pig anti-ovalbumin sera obtained by immunization with ovalbumin emulsified in Freund's complete adjuvant were found to contain non-precipitating antibodies, while their contents varied depending on the groups of animals. For elucidating immunochemical properties of non-precipitating antibodies, 7Sγ1 and 7S γ2-globulins were purified from several lots of antisera, and these antibodies were studied with regard to proportion of non-precipitating antibody, passive hemagglutination, complement fixation and passive cutaneous anaphylactic activities. All the antibody preparations so far tested were found to contain non-precipitating antibody except one preparation of 7S γ1-antibody. There was no evidence that a physico-chemically distinct type of immunoglobulin was responsible for the non-precipitating character of antiserum. Concerning other properties as antibody, any difference could not be observed between the non-precipitating and precipitating antibodies, when antibodies of the same immunoglobulin class were compared with each other. On the basis of these observations, immunochemical properties of guinea pig non-precipitating antibodies to ovalbumin were discussed.