The Southern 100 says it's doubled the number of visitors to the event in just six years - and it's now worth £1.4 million a year to the Manx economy.
A survey by Douglas-based research company Carse Hannay this year showed 3,200 visitors came to the Island for the event - twice the number reported in a 2010 study.
The exercise was carried out for the Department of Economic Development as part of efforts to discover the economic impact of motorsport.
Phil Edge from the Southern 100 Club says it shows the event's profile is growing even if it's sometimes overshadowed by the TT:
Safer Food, Better Business workshop in September
FSA release updates for insurance sector
Government wants your views on Manx food and drink
More time for commercial customers to give feedback on gas laws
Manx farmers and food producers eligible for £20,000 prize from Jersey
Business Isle of Man on the lookout for new chief executive
Port Erin brewery launches tours
Charity to host tech event for children
