The first electricity has been produced from Scottish and Southern Energy's Clyde wind farm in South Lanarkshire.
The Perth-based company said the first turbine had been "energised" and the electricity exported to the national grid.
With 152 turbines, the wind farm will be Europe's biggest, with the potential to power 279,000 homes.
The first of the wind farm's three sections should be finished by the end of this year and the rest by 2012.
Scottish and Southern (SSE) said the turbine could only be started after agreeing certain arrangements with the air traffic control body NATs over the safety of aircraft in the area while a permanent new radar site is being set up.
Colin Hood, chief operating officer of SSE, said: "Clyde is an important project for SSE and for the achievement of wider renewable energy targets and first generation of electricity from the wind farm is a key milestone."
He added: "Reaching these milestones illustrates again the increasing momentum in delivery of SSE's large capital projects. It is momentum we're committed to maintaining."
SSE said the wind farm represented an investment of £500m. More than £200m worth of contracts have been awarded to Scottish companies.
More than 200 construction jobs are being created while the wind farm is being built and after it is up and running 30 people will be employed to operate and maintain the site.