Joint and muscle pain have been reported with quinolones; however, arthropathies induced by quinolones do not result in erosive changes in humans, although such changes have occurred in animal studies. We report an unusual case of destructive polyarthropathy in a 17-year-old boy after treatment with pefloxacin 800 mg/day for 3 months. Pefloxacin may have accentuated the cartilage damage in this case, even if an underlying joint disease could not be excluded.