 In 10 June 2011, the Isap company which operated the line from 1976 to 2011, merged into Stasy S.A.

Line 1 connects the port of Piraeus with the northern suburb of Kifissia.It is built to and is electrified using the 750 V DC, third rail, top contact system, also used by Lines 2 and 3.From Piraeus the line runs eastwards to Faliro and then north to Moschato, Kallithea, Tavros, Petralona, Thisio, Monastiraki, Omonoia, Victoria and Attiki.