• Daytona Prototype (DP): This class was introduced to replace the two existing Sports Racing Prototype groups. To control costs, the cars used a tube frame chassis rather than the expensive composites used to construct most prototype race cars. Also, expenses were contained by limiting modifications and implementing rules that would be in place for five years. Approved to produce the first generation of Daytona Prototypes - for a cost of approximately $400,000 were: Riley Technologies, Doran Designs, Crawford Race Cars, Fabcar Engineering, Chase Competition Engineering, Picchio and Multimatic. Costs were also controlled by restricting the engines to production based motors supplied by Pontiac, Lexus, BMW, Porsche, Ford and Infiniti. Engine displacement was used to determine the weight of a car and whether a five or six-speed transmission could be utilized.
• Sportsracing Prototype II (SRP II): These are purpose built open cockpit race cars from manufacturers such as Lola, Kudzu, Pilbeam and Piccio. The engines used in SRP II cannot be turbocharged and are limited to a displacement of three-litres. The maximum weight for cars in the class it 1,750-pounds.
• Grand Touring Super (GTS): In 2003, the class was expanded to include cars that formally competed in American GT. As a result, there were two sets of rules to accommodate Unibody and Tube-Frame vehicles. Overall the production based Unibody cars were lighter than their Tube-Frame counterparts. Normally aspirated and turbocharged engines were permitted for the Unibody vehicles were as the Tubeframe cars were limited to an iron or aluminum V8 engine with a maximum displacement of 375-cu.in..
• Grand Touring (GT): This category is for production based vehicles such as the BMW M3, Chevrolet Corvette, Ferrari 360GT and Porsche GT3RS. Turbocharging is not allowed and maximum engine displacement is 6.0-liters.

As in the past, the season opened in February with the Rolex 24 at Daytona International Speedway and ended at the same track in November. In between these two weekends, there were events at Homestead-Miami, Phoenix International Raceway, Barber Motorsports Park, California Speedway, Watkins Glen, Mid-Ohio Sports Car Course, Mont-Tremblant and Virginia International Raceway. There was a total of twelve events with the series competing at Watkins Glen twice and Daytona three times.

Watkins Glen International was race six of the twelve rounds contested during the 2003 Grand-Am championship. It was one of the longer events on the schedule at six hours in length. The first six-hour contest was held in 1968 for the International Championship of Makes. The endurance race, was an annual event until the track encountered financial difficulties in 1982. With new ownership in place, the facility began hosting shorter endurance events, until 1996 when the six-hour race returned and became a permanent fixture on Watkins Glen’s Calendar.

In 2003, the first year of the class restructuring, it was difficult for the Grand Am series to achieve the same number of entries as they had in previous years. To improve the situation, the grids were supplemented with cars from the Grand Am Cup championship. There was a total of twenty-five entries at Watkins Glen (5-Daytona Prototypes, 2-Sportsracing Prototype IIs, 5- GTS and 13-GT – nine of which were from the Grand Am Cup series).

The event was impacted by steady rain on Saturday. This weather condition caused Grand Am officials to cancel qualifying and the grid for the race was determined by Owner’s points. With a few exceptions, the starting line-up was similar to the practice times posted by competitors.