Murine interferons induced by viruses and by non-viral substances such as lectins, tilorone, [Escherichia coli] lipopolysaccharide and Brucella were analyzed by affinity chromatography on a column of Sepharose coupled to antiviral interferon antibodies. Virus and B[bone marrow-derived]-cell stimulants probably induced interferons which are antigenically related. T [thymus-derived] cell-dependent mitogens apparently induce an interferon-like molecule which appears to be antigenically and physicochemically different.