Work With A Professional Dog Trainer
If you're not looking at a medical reason for your dog's behavior, the next logical step is to work with a professional dog trainer. A professional dog trainer can act as something of a behavioral psychologist for your dog, looking at aggressive behaviors, diagnosing the cause, and providing training that will help your dog rein in those aggressive instincts. Working with a trainer is often as much about training the owner as it is about training the pet, though, as a good pet trainer will help you to learn new ways to communicate with your dog and help you stop those problematic behaviors that can lead to your dog becoming more aggressive.
Read more about treating aggressive behavior in dogs now.