Revista da Sociedade Brasileira de Medicina Tropical 46(5):641-644, Sep-Oct, 2013http://dx.doi. org/10.1590/0037-8682-1518-2013 A n outbreak of Portuguese ABSTRACT Introduction: Portuguese man-of-war, Physalia physalis (Linnaeus, 1758), are cnidarians capable of discharging intracellular organelles fi lled with venom, resulting in severe envenomation in humans. Methods: We report the clinical and therapeutic aspects of 331 accidents involving Portuguese man-of-war in an outbreak on the coast of the State of São Paulo, Brazil. Results:The clinical manifestations of envenomation were rare and mild and mostly local, systemic reactions; there was a low rate of late complications. Conclusions: The consequences of envenomation were of moderate severity, and fi rst aid measures were effective in controlling the pain. Outbreaks of accidents involving Portuguese man-of-war occur periodically in the area without a clear explanation.