In their current form, the Grand Tours are held over three consecutive weeks and typically include two rest days near the end of the first and second week. The stages are a mix of long massed start races (sometimes including mountain and hill climbs and descents; others are flat stages favoring those with a sprint finish), as well as individual and team time trials and non-competitive exhibition and rest days. Unlike most one-day races, stages in the Grand Tours are generally under 200 kilometers in length.
Controversy often surrounds which teams are invited to the event. Typically, the Union Cycliste Internationale (International Cycling Union) prefers top-rated professional teams to enter, while operators of the Grand Tours often want teams based in their country or those unlikely to cause controversy. From 2005 to 2007, organisers had to accept all ProTour teams, leaving only two wildcard teams per Tour. However, the Unibet team, a ProTour team normally guaranteed entry, was banned from the three Grand Tours due to gambling advertising laws. In 2008, following numerous doping scandals, some teams were refused entry to the Grand Tours: Astana did not compete at the 2008 Tour de France and Team Columbia did not compete at the 2008 Vuelta a España. Since 2011, under the UCI World Tour rules, all ProTour teams are guaranteed a place in all three events, and obliged to participate.
The prizes include the individual general classification, the team classification, the King of the Mountains, the points classification, and often the best young rider classification, in addition to other less known classifications. The most contested ones are the individual general classification (general classification in the Tour de France, general classification in the Giro d'Italia, and general classification in the Vuelta a España) ; king of the mountains classification (mountains classification in the Tour de France, mountains classification in the Giro d'Italia, and mountains classification in the Vuelta a España); and points classification (points classification in the Tour de France, points classification in the Giro d'Italia, and points classification in the Vuelta a España). Only three riders have won all three in the same race: Eddy Merckx in the 1968 Giro d'Italia and 1969 Tour de France, Tony Rominger in the 1993 Vuelta a España and Laurent Jalabert in the 1995 Vuelta a España.
It is rare for cyclists to ride all grand tours in the same year; in 2004, 474 cyclists started in at least one of the grand tours, 68 of them rode two Grand Tours and only two cyclists started in all three grand tours. It is not unusual for sprinters and their leadout men, who do not expect to complete each race, to start each of the Grand Tours and aim for stage wins before the most difficult stages occur. Alessandro Petacchi and Mark Cavendish started all three Grand Tours in 2010 and 2011, respectively, as did some of their preferred support riders. For both riders in both years, only the Tour de France was ridden to its conclusion.
Over the years, 32 riders have completed all three Grand Tours in one year. Of these, Adam Hansen is the only one to do so five times. Marino Lejarreta has done it four times, Bernardo Ruiz three times, Eduardo Chozas and Carlos Sastre twice each, and 27 more riders have achieved the feat once.
The only riders to have finished in the top 10 in each of the three tours during the same year are Raphaël Géminiani in 1955 and Gastone Nencini in 1957.
Three countries have won all three Grand Tours in the same year: France (1964), Spain (2008) and Great Britain (2018). However, Great Britain is the only country out of the three to do it with three different riders.