[Nancy1999]

Can't you fence the yard or get an X-pen. Never take them outside without a leash, especially if they haven't been fixed. I know it's inconvenient, but aren't they worth it? Something gets their attention, and they're off, so hard to catch, and if you run after them, they think it's a game. If they get in the street, they are so hard to see. If another dog catches them -- yorkies don't back down easily.

I wouldn't use an electric fense, it takes lots of training, plus I think it sends them a terrible message.