I'm completely shocked and confused. My 3 year old Labrador has just bitten someone we know in the village having never shown aggressive behaviour before. He runs around outside a lot during the day (in a very excitable manner, he's an overgrown puppy) and we have a gate at the bottom of the drive that is set back from the road. When we're around, we invite people to say hi to Archie through the gate with cheers of 'oh he's fine, he's just very excited and over friendly, he just wants to play.' This again happened today and when the person came to the gate, Archie's tail stopped wagging, and then a very quick growl and a bite. It took a fair chunk off the knuckles which makes me think that he approached with a fist. I didn't see this but this is a report from my Dad who was there. It is very out of character for Archie and we're shocked and upset that this has happened. We're not worried about liability or anything like that - my first reaction to this kind of thing is not oh God we're going to get sued but, is the victim OK, and what the hell do we do about our dog and prevent this from happening again? 1. There was a short growl before the bite. This means it was not a misjudgment/accident by an overkeen dog that still behaves a bit like a puppy 2. He's has never shown aggression before 3. He was not shouted at at the time because Dad was just in complete shock and attending to the victim so Archie has gone unpunished. Any telling off now would be unassociated. 4. The visitor did not approach in any kind of threatening manner - we can't work out why he lashed out like this. I guess my question is, what the hell do we do now? Is this a blip? Or do we have to take measures because our dog has had a fundamental change in behaviour?