[JULIEGRAHAM]

My Three Yr Old Male Lab Is Not Neut. And Has Recently Started Growling And Attempting To Bite People And It Ranges From Small Children That He Has Never Seen To Adult Men And Women He Has Not Seen Before , And Its Immediately When He Sees Them. He Is And Has Always Been A Great Dog, Friendly , Loves To Play, What Could Have Changed And What Do We Do To Stop This

[carolbcac]

It's hard to say what may have triggered this; any correlations with on/off his property, on/off leash, whether he had some sort of scary encounter when he was alone (being surprised by a meter man coming around the house, children teasing him through the fence, etc.) He could generalize fear of one type of person to all people.
Observe his body posture--is he totally leaning forward, trying to get to the person, or sort of waffling back and forth with his ears back and being defensive?
First off, take him to the vet to rule out any sort of medical problem. If he has hip dysplasia or some other painful problem, the aggression could be from fear of getting hurt. Dogs with low thyroid levels sometimes develop aggression problems.
If he is healthy, have him neutered. It may not totally fix the problem but should help calm him down.
Find a local trainer or behaviorist with a good reputation with aggression cases. He is at the age where young males tend to start trying to take over top position in the pack, (Think teenage boy with way too many hormones and way too little self-control) so this needs to be nipped in the bud.