Tosufloxacin tosylate (TOSU) and temafloxacin hydrochloride (TEMA) were tested in vitro against 248 clinical isolates of various species of streptococci recovered in a hospital microbiology laboratory (Bellevue Regional Teaching Hospital). Species included S. pneumoniae (n = 20), group A streptococci (n = 22), group B streptococci (n = 30), group G streptococci (n = 17), group D S. bovis (n = 19), Enterococcus faecium (n = 45), Enterococcus faecalis (n = 28), S. sanguis (n = 21), S. milleri (n = 29) and S. mitis (n = 17). Activities of each of the two study drugs were evaluated comparatively with two other fluoroquinolones, i.e., ciprofloxacin (CIP) and pefloxacin (PEF). Activities of each of these four antibiotics, expressed as the MIC 90%, varied as follows according to the species of streptococci: TOSU, 0.25 to 1 mg/l, TEMA 0.5 to 2 mg/l, CIP, 1 to 4 mg/l and PEF 8 to 32 mgl. Overall, TOSU and TEMA exhibited the greatest activity of the various species. The size of the inoculum had no significant effect on MIC values.