Labrador Retrievers are currently the most popular breed used for Guide dogs. Most programs use Labrador Retrievers, Golden Retrievers, German Shepherds, or crosses between Golden Retrievers and Labrador Retrievers as guide dog candidates. Some programs use Labradoodles, Boxers, or Chesapeake Bay Retrievers. It is extremely rare for a private trainer to train a guide dog. Since very few programs would accept outside animals for training, other breeds are very difficult to obtain.
These breeds are chosen for their biddability, intelligence, ability and willingness to work long hours, ability to tolerate stress, good health, and public acceptability or recognition.
Originally guide dogs were primarily German Shepherds. They were selected because they were available (this was right after World War I), they were being very well bred to work, could work very long hours, were easy to train, and were good at working out problems or situations for which they were not trained.
Later most programs switched to Labrador Retrievers because the German Shepherds were not suited for many clients. Shepherds require confident owners with some skill at training and handling dogs. They can be hard headed and become destructive if not given enough mental and physical stimulation. In more recent years their public image has also deteriorated because of poorly trained dogs biting people.