One of the most important care of transmission's gas operator is to operate its gas network system in the very best conditions, i.e. running its system safely and reliably, taking into account the protection of the environment. This aim, is obtained by undertaking a very sever safety rules and codes in the design, construction & testing, operation and Maintenance of the gas transmission network. The Algerian's company of Gas Transmission network administration "GRTG", is operating more than 13 800 km (more than 8 500 miles) gas pipeline network and related facilities, for national's consumption purpose. Among this total gas network's length, 19 % of the pipelines are aged over 30 years old (the oldest ones are greater than 50 years old). In consideration of this factor, GRTG implement special programs for ageing pipelines which across high population density areas in order to evaluate the actual pipeline condition in operation. These programs planned for short and long term, deal with monitoring, preventive and corrective maintenance and are scheduled monthly, quarterly and yearly. The present communication shows us the GRTG's experience in implementing programs for ageing pipelines, to mitigate the risk of pipeline failure (leak/rupture) or damage. These programs consist of: (i) In line inspection (inspection by intelligent tool) (i) On line Inspection (CIPS-DCVG + cathodic protection history's data). (i) Metallurgy, Mechanical and Hydrostatic tests over gas pipeline's test-tube (test-tube taken from the most sever part of a gas pipeline affected by corrosion points). The chosen gas pipelines which will be discussed by the communication are those obtained from the works done on the following gas pipelines: - ⋄ 0 14"'-16"-20" Bir el Djir - Ravin Blanc (Oran):4,85 km - age > 50 years old (unpiggable) - ⋄ 016" Gue Port -Alger (Algiers): 11,3 Km - age > 50 years old(piggable) - ⋄ 14" Ain el Biya-Bir El Djir (Oran): 29 km - age > 50 years old(piggable) - ⋄ 8" Hadjar Essoud (Annaba): 2,9 Km - age 38 years old(un-piggable) The obtained results from different programs are illustrated by photos, tables and texts; time and costs were evaluated. Finally conclusion and recommendations will be given for transmission gas operators, who are interested to inspire with these presented works.