A case of botryomycosis was studied in which a coagulase-negative, DNAsenegative Staphylococcus with wide antibiotic sensitivity in vitro was isolated and which could be classified as having a 'low pathogenic capacity'. Nevertheless, there was no improvement with appropriate therapy. IgG and complement (C3) were demonstrated in the grains. Botryomycosis can be considered as a state of 'equilibrium' between the host and the microorganism. It is not clear if this results from low pathogenicity of the organism or from some peculiar characteristic of the host.