If you feed him a high quality dog food, it is not necessary to supplement his food with a multivitamin. However, GNC makes a good multivitamin for dogs.
In general, dogs don't need multivitamins if their food is AAFCO approved for their life stage. Canine PLus by Vetri Science would be fine for most dogs though.
Pet Natural's Daily Best is supposed to be one of the best multivitamins for dogs. Most multivitamins for dogs are sold depending on dog's age as puppies, seniors, etc.
Talk to your vet about your dog's specific needs in a multivitamin. Different dogs have different needs and will require different vitamins. Factors can include age, health, breed, if the dog has any chronic problems, etc.
