Five species of mycobacteria were stained by Ziehl-Neelsen, Kinyoun and Auramine-Rhodamine after either routine autoclaving, or exposure to rifabutin and ciprofloxacin. Organisms from each treatment group were stained and compared to viable controls. ATCC strains and fresh clinical isolates of all five species were evaluated. All species in both treatment protocols presented similar staining characteristics. Viability of mycobacteria, therefore, must be established by culture.