Construction work on Gloucestershire Police's new headquarters is due to begin on Thursday.
The building, on Waterwells Business Park in Quedgeley, will be completed by the end of 2005.
A total of 400 people will be based at the site, which is needed because the force has outgrown its current base in Lansdown Road, Cheltenham.
A ceremony will be held at midday on Thursday to mark the start of work on the building.
At present, the force's departments are housed in a number of out-of-date premises scattered across four different locations, but once work is finished they will all move to the new site.
The project is funded by a Private Finance Initiative (PFI).