The supply of natural gas in Slovenia began in 1974 with the signing of an agreement to pool funds to implement a programme to supply natural gas to Slovenia. Construction of the gas transmission network began in 1977. A year later, the network was put into use with the supply of the first customers in Slovenia and for transmission to Croatia. Natural gas comes from a source in Russia. Over the years, the gas transmission network has been expanded, such that natural gas is present in all major Slovenian industrial centres and cities, while the reliability of supply has reached a high level. The next major milestone was achieved in 2004 when the liberalisation of the Slovenian market began.
