[BostonRott]

I tell my puppy owners to wait until 18-24 months.

Neutering a male at 6 months WILL change his growth potential. He will not develop the secondary looks of a mature, in-tact male (i.e. thicker neck, filled-out chest, broad head). Males who are neutered young tend to be very tall and weedy looking.

There are studies done in Rottweilers which strongly link early neutering (under 17mos of age is defined as "early") to high risk of osteosarcoma (bone cancer, which is VERY prevalent in this breed).

My personal recommendation: wait a year. It's not very hard to keep a boy away from the girls (leashes are such magical things). People really blow out of proportion males trying to "get at" females in heat. And with today's rates of spay/neuter, it's not like there are females in heat on every corner. Most dogs are neutered.