The first case of Legionella micdadei (Pittsburgh Pneumonia Agent) infection in Sweden is presented. A previously healthy 68-yr-old man fell ill with diarrhoea, fever, and mental confusion. Subsequently chest roentgenography revealed pneumonic infiltrates and a seroconversion to L. micdadei was shown. No source or transmission of infection was established. The only notable event was that the patient had been drinking rain-water from a barrel 1 day prior to his illness. An alimentary route of infection was considered.