The results of long term treatment with griseofulvin are reported in 54 patients with dermatomycoses, especially of the hands and feet with nail involvement. After treatment, the length of observation varied between one and one and a half years. In 39 cases there was no relapse; in 15 cases there was relapse with clinical signs and with the fungus found microscopically. In 6 patients a latent and noninflammatory mycosis developed in which the patients had only minor signs but in which microscopic examination for fungi was positive. Mycoses treated with griseofulvin need careful observation and follow-up.