Casado lost the race leader's maglia rosa (English: pink jersey) after stage 2a that contained a mountainous course.

Twenty teams were invited by the race organizers to participate in the 1991 edition of the Giro d'Italia, ten of which were based outside of Italy.

[8] The teams entering the race were:[1][9] The starting peloton did include the previous year's winner Gianni Bugno.

[10][13][11][14] Mario Cipollini, despite a poor showing that Tour de Romandie, was viewed as the sprinter to watch for the estimated ten stages that could result in a bunch sprint.

[13] Notable absences included 1988 winner Andrew Hampsten, Dutch rider Erik Breukink, and Maurizio Fondriest.

[13] The route for the 1991 edition of the Giro d'Italia was revealed to the public on television by head organizer Vincenzo Torriani, on 1 December 1990.

[24] The queen stage was thought to be twelfth leg from Savona to Pian del Re as the final climb was 18.5 km (11 mi) at an average gradient of 7.5%.

[13] During the first stage, Alberto Leanizbarrutia attacked on his own and led the race for 150 km (93 mi) before being caught by the chasing peloton within the final ten kilometers.

[27] Reigning winner Gianni Bugno won the trans-alpine morning stage ahead of other main contenders.

[27] This stage saw the race leader's maglia rosa (English: pink jersey) switch from Casado to Franco Chioccioli.

[27][28] Gianluca Pierobon of ZG Mobili team won the afternoon time trial by five seconds over Spaniard Marino Lejarreta.

[30] Boyer went on to win the stage by twenty-three seconds over the chasing peloton, gaining enough time to earn the race lead.

[32] On the final climb of the day, Iñaki Gastón and Leonardo Sierra attacked with eight kilometers to go but were caught by the chasing riders.

[32] Gaston attacked again with a kilometer remaining, but was robbed of the stage win as Vladimir Poulnikov overtook him three meters before the finish.

[34] Despite the best efforts of the chasing peloton, the breakaway group survived and saw Ari-Ceramiche Ariostea's Davide Cassani take the stage by edging out Mario Mantova.

[37] After an unsuccessful breakaway attempt by fifteen riders,[37] Maximilian Sciandri, LeMond, and Michele Coppolillo attacked and formed a group off the front.

[38] Sciandri and LeMond crossed the line in first and second, respectively, while Coppolillo was caught by the peloton in the closing meters of the stage.

[39] The group of main contenders reached the final climb together, with Banesto's Jean-François Bernard launching the first attack which saw him gain a maximum advantage of around thirty seconds.

[39] The next to make a serious effort was Lejarreta, who was followed by Chioccioli, Massimiliano Lelli, and Sierra, who attacked with ten kilometers left in the stage.

[8][39] The thirteenth leg of the race featured two ascents of the Alpine mountain Sestriere, the second of which served as the finish for the day.

[40] With twenty kilometers to go in the fourteenth leg, Franco Ballerini, Casado, Juan Martínez Oliver, and Brian Peterson formed a breakaway group.

[8][42] He rode the remaining fifty kilometers on his own to the stage victory, with his lead expanding to at most two minutes thirty seconds.

[43] The top five riders in the general classification formed a leading group on the final climb but there were no major moves to create time gaps.

[43] The following day was the last in the Dolomites and saw the ascension of five major climbs, including the Cima Coppi Passo Pordoi.

[44] The nineteenth leg featured only one categorized climb, which Iñaki Gastón won to seal his victory in the mountains classification.

[45] The penultimate stage of the race was a 66 km (41 mi) individual time trial that contained one un-categorized climb within the route.

[46] Race leader Chioccioli took the course and at the first time check at 15.5 km (10 mi) he had already put thirty seconds into Bugno.