Viridans streptococci continue to be the most common etiologic agents in bacterial endocarditis. The spectrum of diseases other than endocarditis caused by these organisms, however, has received sparse attention. Moreover, little clinical information is available concerning the individual viridans streptococcal species. During the 16 months of this study, one species of viridans streptococci, Streptococcus milleri, caused a surprising number of clinically significant suppurative infections. Clinical syndromes included the following: abscesses, 10 cases; peritonitis, four cases; endocarditis, three cases; cholangitis, empyema and cellulitis, one case each. A gastrointestinal source was apparent in eight of these 20 cases. Review of 58 cases of viridans streptococcal endocarditis demonstrated that although Strep. milleri was an infrequent cause of endocarditis, this species was associated with an unusual frequency of suppurative complications. Our experience suggests that Strep. milleri may be more commonly associated with serious suppurative infections than other viridans streptococci and that species identification may be a clinically useful procedure.