The historic development in the urban transport of Thessaloniki, followed the parallel route of Thessaloniki and the great events that marked the passed century.

More modern, more dynamic, with new ideas each day, O.A.S.TH. tries for the best it can offer to the passenger.

In spite of that, it cannot forget the memories recorded in the primary form of Thessaloniki’s transport because water flowed in the river of history and from the horse-driven carriages to today’s state-of-the-art buses with all the comforts to the anti-pollution technology that is friendly to the environment.

So, in 1879 a Belgian company takes over the transport of passengers with carriages of 4-5 seats.

From 1905 the carriages of 15-20 seats move on iron-tracks.

In 1908, the Belgian company that took over the electrification and organization of the city’s transport, organizes and circulates the wheel-tracks under the name ``Wheel-track and Electricity Corporation``. The first lines of wheel-tracks in the line Apothiki (Eksoxon) – Limani and the line Hirs (today Ippokratio hospital)- Behchinar (26th October).

With the settling of the refugees in the city and the creation of refugee compounds and the significant increase of population appear for the first time around 1927 for the first time, the lines Ermou- Pano and Kato Toumba.

During 1930-35 new cars of 20-25 seats start circulating, moving parallel to the wheel-tracks and in competitive relationship to them.

In 1936, with legislation was created the common management that took over the Bus lines.

In 1940 the city already had 150 city buses of 40 seats owned by private drivers . At the same time, there is a buyout of the Belgian corporation by the State and the ``State exploitation of wheel-tracks and electrification of Thessaloniki`` is created (K.E.T.H.Θ).

During the WWII and the occupation in Greece, all buses are recruited and destroyed. All transport is done only with the Tram lines.

In 1947 is the creation of KTEL which take over the service of Thessaloniki allocating it in 3 sectors . 243 old and repaired buses are put in circulation from which in 1949 170 are replaced with new ones. In 1952 the 3 groups of bus owners merge into one creating K.T.E.A.Λ.Θ with a total of 243 buses. The wheel-tracks are taken over by "State exploitation of wheel-tracks of Thessaloniki" (KETΘ) whilst the lighting sector is given to ΔΕΗ.

Ιn 1957 O.A.S.TH. is founded with the legislative decree 3721, giving it the exclusive city transport service of Thessaloniki after a pertaining agreement with the State. Simultaneously, the wheel-tracks are abolished and Trams are put out of circulation. During this time, O.A.S.TH. has 283 buses of 60 and 80 seats.

From 1963 until 1977 283 new buses are of 100 seats are put in circulation.

In 1978, O.A.S.TH. obtain the first linked buses in Greece of 150 seats.

In 1979 expands with the law 866/79 the urban transport in the suburban areas of Thessaloniki following the merging part of the KTEL of Thessaloniki and simultaneous expansion of the agreement with the State until the year 2000. At the same time, stops another form of semi-urban transport done by small boats, filling mainly tourist needs during summer months with the shoreline areas Aretsou-Peraia-Agia Triada.

At 30th April 2001, with law 2898/2001 the third financial agreement between the Greek state and O.A.S.TH was signed, valid until 2009.

At 4th August 2003, an additional financial agreement between the Greek state and O.A.S.TH was signed, valid again until 2009 and the jurisdiction of O.A.S.TH was expanded in 15 new municipalities (Kalitheas, Ag. Athanasiou, Halastras, Axiou, Halkidonas, Koufalion, Migdonias, Assirou, Lahana, Lagada, Koronias, Thermis, Vasilikon, Mikras, Epanomis). Also 12 new bus routes were established and 48 new buses were added to the fleet of O.A.S.TH.

On the 11th Jan of 2008 the fourth financial agreement between the Greek government and O.A.S.TH. was signed, with which the fleet number of O.A.S.TH. increased by 64 to a total of 600 and the concession of public bus transport was extended up to 2 years after the completion of the subway construction works (M.E.T.R.O.) and its extensions.