From Germany, Austria and Switzerland
Take the train via Innsbruck and the Brennero/Brenner pass to Bolzano/Bozen or Fortezza/Franzensfeste, where the direct Alta Badia Bus shuttle service operates; bookings can be made online.
As an alternative from Fortezza/Franzensfeste, change to the train to San Lorenzo/St. Lorenzen in Val Pusteria/Pustertal. Here, take the bus no. 460 going to Colfosco/Kolfuschg and get out in La Villa/Stern (Alta Badia); here change to bus no. 465, which will take you to San Cassiano/St. Kassian.
If you are coming from east, take the train to San Lorenzo/St. Lorenzen in Val Pusteria/Pustertal and travel on to San Cassiano/St. Kassian as described above.
From other regions in Italy
If you are coming from south, take the train via Verona, Trento to Bolzano/Bozen or Fortezza/Franzensfeste, where the direct Alta Badia Bus shuttle service operates; bookings can be made online.