Came here to ask this question. Our boy is almost 9 months, and almost 60 pounds. Vet recommended waiting until 18 months to 2 years, but we are seeing some issues and wondering if it would be better to do it sooner? As someone else said, other neutered male dogs sometimes get more aggressive, we've noticed. He was bitten by another male dog at the park a few weeks ago requiring stitches. We have an almost 3 year old female (spayed), and in the last month or so he often tries to mount her, usually when he's wound up. She's pretty tolerant but has growled and snapped at him when she's had enough and he backs off. He is also very high energy, and is a lot to keep up with. While he's not neutered he can't go to day care, which is pretty disappointing. We have a wonderful day care that our female loves, and I really wish he could go. So we are contemplating perhaps having him neutered around a year. I have been reading about the more recent research on this issue, and I am not seeing a lot that makes me think waiting beyond a year is really going to be risky as far as preventing future cancer and other issues. Someone suggested taking him in for an x-ray to see about the status of the growth plates. Don't know if that's possible. Would appreciate any thoughts or experiences on this.