A new passive agglutination method is reported.Large, very heavy, uniform latex particles coated with antigens or antibodies were mixed with corresponding antibodies or antigens in reacting wells of an appropriate shape and size. Agglutination results were read after 30 min of continuous rotation at a suitable speed. With this simple and rapid continuously rotating passive agglutination method, we could detect antidinitrophenol monoclonal antibodies, natural anti-dinitrophenol antibodies, rheumatoid factor, allergic antibody to tick, human chorionic gonadotrophin and human IgE. This method is suitable to detect weak and small quantities of antibodies in a brief time.