Histoplasmosis is a systemic mycosis prevalent in the Americas. Humans become infected via the respiratory route by inhaling aerosols from soil contaminated with bird and bat excretions. Acute pulmonary histoplasmosis is usually asymptomatic and is more often a self-limiting illness. We report a series of seven acute pulmonary cases in adults during an outbreak in Nova Friburgo city, Rio de Janeiro State, Brazil, in a group of volunteers who were cleaning an old, abandoned house without using personal protective equipment. The patients had a favorable evolution after suitable treatment, but all required hospitalization.