The influence of butyl 6alpha-fluoro-11beta-hydroxy-16alpha-methyl-3,20-dioxo-1,4-pregnadien-21-oate (fluocortin butylester, Vaspit), a new corticosteroidal compound with a marked dissociation between local antiinflammatory and systemic action, upon resistance against infections was studied in experimental bacterial and fungal infections in mice. The results of the experiments showed, that fluocortin butylester, even after repeated s.c. or oral administration of dosages up to 100 mg/kg did not depress the resistance of the animals against microbial infections. The relevance of the animal models was checked by parallel experiments with fluocortolone, hydrocortisone, prednisolone and cyclophosphamide.