The in vitro activity of a new fluoroquinolone, tosufloxacin (T-3262), against 111 pathogenic Nocardia strains was studied by an agar dilution method and compared with the activities of other fluoroquinolones. All strains were susceptible to tosufloxacin, and the drug was 2 to 20 times more active than four other quinolones tested. Nocardia farcinica was the Nocardia species most susceptible to tosufloxacin.