It was a series for Le Mans Prototypes (LMP) and Grand Touring (GT) race cars divided into 4 classes: LMP1, LMP2, GT1, and GT2.
Among the biggest announcements prior to the start of the 2006 season was that Audi would continue their involvement in the ALMS with their new R10 TDI diesel engined LMP1 with the car making its international racing debut at the 12 Hours of Sebring in preparation for Le Mans.
Fellow LMP1 competitors Dyson Racing also announced an upgrade from their troublesome Lola EX257s to brand new B06/10s with the new AER Turbo V8 engine unit.
The involvement of Maserati in the series was also pulled due to the cancelling of the project by the corporate heads since it never reached its initial plans, and the continued restrictions put in place by IMSA.
The ALMS also created a new class of competitors, known as GT2S, designed to allow racing cars based on production vehicles which had seats for four in a coupe or sedan body style.
First, to replace the earlier round at Road Atlanta held soon after Sebring, a new temporary street circuit near Houston's Reliant Park was announced in cooperation with Champ Car.