We present evidence that Earvin “Magic” Johnson's announcement that he contracted HIV served as a public-health catalyst for rapidly correcting the public's understanding of who was at risk of infection. Using a novel identification strategy, we present evidence that there was a large but temporary increase in the number of AIDS diagnoses for heterosexual men following the announcement. This effect was concentrated in areas with greater prior exposure to Johnson. We show that these men were both more likely to have been diagnosed via a formal blood test and less likely to die within 1 decade of their initial diagnosis—suggesting that Johnson's announcement caused an intertemporal substitution in testing which prolonged patients' lifespans as a result of earlier access to medical care. We estimate that Johnson's announcement caused approximately 800 additional heterosexual males in the United States in metropolitan statistical areas with National Basketball Association franchises men to discover their underlying AIDS diagnosis and, of whom, were more likely to live at least 1 decade beyond their initial diagnosis date.