Standing for 'International Race of Champions' this automobile racing series is somewhat similar to NASCAR. The IROC racing series started in 1974, first racing Porsches, prepared by Robert Penske. After one season of racing, Penske realized the cost to maintain the Porsches for racing was to expensive and the following year (1975), switched to the Chevrolet Camaro. IROC used the Chevrolet Camaro from 1975 to 1991. In 1985 Chevrolet and IROC entered into a licensing agreement which resulted in Chevrolet obtaining the right to use the IROC name on its production Camaros.
Thus in 1985, The Chevrolet Camaro made its first public appearance - the IROC-Z model - an add-on option package to the 1985 Camaro Z28. This car was produced for a little over 5 years, with only 166,976 ever being built. By the beginning of the 1990 the last of the IROC-Z's were produced as Chevrolet's licensing/sponsorship
agreement expired and Chevrolet made the decision not to renew it. Because of this expiration and nonrenewal, Chevrolet had to immediately stop production of the IROC-Z and reintroduce the Z28 as the performance model of the Camaro lineup. Due to the limit number of vehicles produced the IROC-Z has now become a legend in the automotive world.
Dodge then replaced Chevrolet as the licensee/sponsor of the IROC racing series. Dodge releasing its own version of an IROC car called the IROC Daytona, named after the Dodge Daytona. This car did not compare to the legendary IROC-Z Camaro, with very few being made and following a lack of public interest production was stopped .
Pontiac replaced Dodge as the primary sponsor leaving the series as it is today. The IROC series currently races the Pontiac Trans AM.