If there is one thing that is clear about the Doctor it is that he needs companionship on his travels. Although he may appear abrupt and unfriendly to newcomers in the TARDIS's crew, it is partly his concern for their safety that makes him reluctant to accept them on board. He quickly becomes fond of his new friends and is sad to see them leave when they choose to go their own way.

The friends and companions of the Doctor listed here are those who have adventured with or known him for longer than one adventure -- people who can truly be considered companions, rather than those who travel only briefly in the TARDIS. Characters such as Sara Kingdom in The Dalek Master Plan, the Trojan slave Katarina from The Myth Makers and Ray from Delta and the Bannermen are not included: they are secondary characters who have helped the Doctor but not gone on to travel with him on other adventures.