We have evaluated the activity of a new fluoroquinolone, trovafloxacin (CP-99,219), against 434 strains; 24 of them are resistant to ciprofloxacin. Against gram-negative bacteria, trovafloxacin has the same activity as the others fluoroquinolones. Against gram-positive bacteria, this antibiotic agent is very active. (MIC = 0.016 to 0.5 microgram/ml); Streptococcus is the most sensitive species. The ciprofloxacin resistant strains are also resistant to trovafloxacin.