Intrathoracic inoculation of mice, kept at a temperature of 25°C–28°C, with 2 × 106 yeast phase of Sporothrix schenckii produced progressive and often fatal infection including dissemination to subcutaneous tissues. This supports the concept that lung can serve as the portal of entry in human sporotrichosis. The contention that S. schenckii can not survive in the warm organs is not upheld by the present study. Intramuscular administration of cortisone acetate in aqueous suspension (2·0 mg in 0·1 ml) given daily into the hind-legs for 5 days before and 3 days after the infection, as well as the presence of Ehrlich solid tumor led to an acceleration of the course and intensity of infection. The role of stress in intensifying the course of experimental disease is pointed out.