Recent studies investigated participation and performance trends in age group half marathoners and full marathoners for a single event. The present study investigated participation and performance trends in age group athletes in all half marathons and full marathons held in a single country during a given period of time. Changes in running performance and age of 226,754 half marathoners and 86,419 full marathoners competing in Switzerland between 2000 and 2010 were analyzed using linear regression analyses. The number of half marathoners increased (P < 0.01) from 2000 to 2010 for both men (+231%) and women (+299%). In contrast, the number of male and female full marathoners increased until 2005 only and decreased thereafter. The greatest part of the finishers of both genders was assigned to age group 40-44 years in half marathons (19.5% of finishers) and full marathons (22.0% of finishers). Running performance of female full marathoners improved in age groups 30-34, 35-39, 40-44, 45-49 and 50-54 years. Running performance of male full marathoners improved in age groups 25-29, 30-34, 35-39, 45-49 and 55-59 years. Female half marathoners achieved no change in running times in all age groups. For male half marathoners in age groups 30-34, 40-44 and 50-54 years, running performance declined. In conclusion, during the 2000-2010 period in Switzerland, it appeared that participation in half marathons increased but running performance stabilized. In contrast, participation in full marathons decreased but running performance improved. Further investigations are required to collect complete data for other countries and the investigation of other endurance events in Switzerland.