This study examines the relative importance of a longer than normal 4-month training period, or being ¿passed back¿ from the original training class to join a class in which dogs are at an earlier stage of their training, on the overall probability that a dog entering guide dog training will ultimately graduate as a guide dog. The study group consisted of dogs that were trained at The Seeing Eye guide dog school in the years 2000 through 2005. In total, 2033 Labrador retrievers (LR), golden retrievers (GR), German shepherds (GS) and Labrador retriever/golden retriever crosses (LGX) were included in the study. Of all dogs, 39% had been passed back during their training, and 56% had graduated as guide dogs. In general, females had a lower chance to be passed back than males, except for GS and LGX. Overall, GS had the highest chance to be passed back during their training. LGX had the highest, and GS the lowest, probability for graduating as guide dogs. Dogs that were passed back for behavioral reasons were only half as likely as dogs completing training normally to work as guide dogs, whereas medical reasons and ¿no match¿ reasons for being passed back hardly influenced the chances to become guide dogs. Overall, the current 4-month standard training program at The Seeing Eye seemed mostly successful for LGX and LR, whereas GS and GR had a higher success rate when being passed back, i.e., they were more likely to graduate as guide dogs when they were trained for a longer period than the standard training program.