An outbreak of acute histoplasmosis occurred in northern Louisiana in September 1977. All 6 men who cleared a field of bamboo cane known to be a blackbird roosting site were affected. All had clinical and roentgenographic findings of acute pulmonary histoplasmosis, and all recovered. Seroconversion of fourfold rise in antibody to Histoplasma capsulatum yeast, or mycelial-form antigens was demonstrated in 5. Immunodiffusion testing showed that all 6 patients developed H. capsulatum M bands, and 2 developed H bands specific for active infection. The H. capsulatum was isolated from the soil in the cane field. This is the first report of an outbreak of histoplasmosis in Louisiana and the first known isolation of H. capsulatum from Louisiana soil.