A 32-year-old male was admitted to our intensive care unit for low cardiac output syndrome. Echocardiography was suggestive of extensive hypokinesia and the ejection fraction was 0.22. Serological tests, including anti-HIV antibodies (ELISA), were negative. The patient was intubated and an intra-aortic balloon pump was inserted. Twenty-four hours after admission a paracorporeal left ventricular assist device (LVAD-MEDOS) was implanted. The left ventricular function showed progressive improvement with normalization of the ejection fraction on day 19. The device was removed on day 20. Before discharge, the patient admitted that he had had unprotected sex with numerous male acquaintances; anti-HIV testing turned positive. The final diagnosis was fulminant myocarditis during HIV seroconversion.