Naftifine, a new antifungal agent belonging chemically to the allylamines, was tested for its in vivo activity after topical application against guinea pig skin infections caused by Trichophyton mentagrophytes, T. mentagrophytes var. quinckeanum, or Microsporum racemosum. Compared with standard compounds, naftifine proved to be highly effective mycologically and clinically after topical application in the above models.