This paper discusses the background in reality of the Heroikos (Dialogue concerning Heroes), which is ascribed to Philostratus of Athens, and is mainly devoted to the hero Protesilaos. After a summary of the work, the paper considers it from four aspects. The time of writing falls after 217 (the second victory at Olympia of the athlete Helix of Phoenicia); there may be a reference to events in Thessaly under the emperor Alexander Severus (222-235). If the author is the well-known Philostratus, then such a date also implies a dramatic date in the author's own time. This is corroborated by two series of references which appear to run from the comparatively recent past to the present. One of these concerns bones of heroes, while the other concerns athletes to whom the hero Protesilaos had given advice in the form of oracles. The geographical setting of the dialogue is Elaious in the Thracian Chersonese. The evidence for the cult of Protesilaos on the territory of Elaious comes from literature, notably Herodotus, from coins of the time of Commodus, and from modern observations, notably a vivid account given by Heinrich Schliemann. While Philostratus' description of the cult-place at Elaious appears very accurate, his account of the Island of Achilles in the Pontus is less so. Finally, the paper considers the Heroikos in the context of contemporary belief about heroes and their powers. Another work probably by the same author, the Life of Apollonius of Tyana, is adduced to assess the credulity of readers in Philostratus' time and later. Documents and literature of the imperial period show that even dead contemporaries could be regarded as heroes, who were still influential even from beyond the grave. The references to Protesilaos in literature (Pausanias, Lucian) strongly suggest that he was regarded as issuing oracles in the form of dreams, and this too accords with beliefs about heroes both in the Hellenistic period and in the Roman.