The biggest change from the current model will be a three-part, painted steel roof from Remscheid, Germany-based supplier Edscha. The first production models of the E93, as the vehicle is known internally, have already begun.
BMW has a newly built construction area that Edscha will lease from the automaker. The sophisticated roof structure will be assembled on site, instead of being delivered from the company's Hengersberg, Germany, plant.
Company sources said between 100 and 160 Edscha workers will be employed at Regensburg. Up to 20 percent will be contract workers.
Edscha has been the supplier for almost all of BMW's convertibles, including current versions of the 3 and 6 series and the Z4 roadster.
Last year, BMW sold 40,300 units of its convertible 3 series worldwide. A total of 9,200 were sold in Germany.
In 2002, the vehicle line's most successful year to date, BMW sold more than 54,000 units.
The notchback version of BMW's top-selling model has been in dealerships since March. The station wagon will follow in 2006, and an M3 version with a V-8 engine in 2008.