Levofloxacin, levo-isomer of the D,L-racemate ofloxacin, is a new fluoroquinolone antibiotic approved for use in the United States in December 1996. It has an extended spectrum of activity compared with older-generation fluoroquinolones (ciprofloxacin, ofloxacin), with improved activity against gram-positive bacteria and excellent activity against gram-negative bacteria and atypical organisms. Although its activity against anaerobic organisms is improved over that of earlier fluoroquinolones, levofloxacin should not be considered a first-line anaerobic agent. It is available in an injectable form, as well as an oral formulation with virtually 100% oral bioavailability. The plasma elimination half-life ranges from 6-8 hours in individuals with normal renal function. Approximately 80% of drug is eliminated unchanged in urine through glomerular filtration and tubular secretion. The pharmacokinetics are not appreciably affected by age, gender, or race when differences in renal function and body mass and composition are taken into account. Levofloxacin had impressive efficacy in clinical studies of community-acquired pneumonia, acute bacterial exacerbations of chronic bronchitis, acute sinusitis, skin and skin structure infections, and complicated urinary tract infections and pyelonephritis. It is well tolerated; its adverse event profile is similar to that of other fluoroquinolones, with gastrointestinal and central nervous system effects reported most commonly. Drug interactions are uncommon with levofloxacin; however, coadministration with antacids or with other agents containing divalent or trivalent cations reduces levofloxacin absorption. The agent should prove to be more effective than older fluoroquinolones, especially for infections caused by pneumococci highly resistant to penicillin.