Severe neutropenia associated with primary HIV infection is unusual. We report the fifth case in a 50-year-old male with a neutrophil count of 500/mm(3) and a platelet count of 92,000/mm(3) at the time of early HIV-1 seroconversion. In all previously published cases and in our case, severe neutropenia was a very early sign of acute HIV infection, and it regressed spontaneously and quickly. HIV testing should be recommended when severe neutropenia is observed, especially in the context of a flu-like or mononucleosis-like infectious syndrome.