Here’s another good article that lays out the amounts that could be deadly in varying size dogs. The upshot of the scientific and anecdotal evidence is that a little milk chocolate given to your German Shepherd is not going to harm the dog. A big slab of baker’s chocolate, or a helping of cocoa powder, could kill your little Maltese terrier. There is no build up of theobromine in the system, it’s just processed slower in dogs than humans – if you fed your St. Bernard half a snickers bar every day, it doesn’t appear that would affect his health or life expectancy at all. However, because it’s difficult to ascertain exactly how much theobromine you are putting in your dog’s system, and because each dog is different, it’s probably best to keep it away from your dog. My large dog gets an occasional dropped cookie or bit of candy, with zero ill effects. But I don’t intentionally feed him chocolate.