Erythres is located at an altitude of 480 m, on the northern foothills of Mount Cithaeron. The town is located 60 km from Athens, on the borderline separating the prefectures of Attica and Boeotia and, more specifically, along the old Athens-Salonica national road. According to the 1861 census, Erythres had 884 inhabitants and was administered, together with the village of Vilia, by the Municipality of Eidyllia. Although the gradual settlement of farmers from Vilia to Erythres began around 1830-1840, the official detachment of the two municipalities took place in 1875. The population of Erythres was steadily growing since 1879, when an official census counted 1,759 residents. The village boasted 2,566 residents in 1896, 3,120 in 1907, and 3,550 in 1981. The gradual population growth meant an increase in the number of people seeking employment in the surrounding area, particularly in the industrial area of Thebes. According to the 2001 census, Erythres has a population of 3,329. The modern town of Erythres features all modern facilities, while retaining its traditional 19th century architecture.