I know I am going to shock a lot of moms out there, but when my oldest was around that age and was using his mouth for ugliness, I took my grandma's advice, and had him hold a bar of soap in his mouth for a few seconds. He stopped that behavior. He only had to do that once more because he used a curse word. He is now 6 and doesn't use his mouth that way anymore. My 3 yr old started calling names and my son warned her not to do it because she wouldn't want soap in her mouth. I've never had to use the soap with my daughter. Some may think that is cruel, but it worked, and sometimes I think we need to get back to how some of our grandparents disciplined....After reading some of the responses, I wanted to edit mine a little. While, I still stick with first part, I like the ideas, and probably have used some that the ladies are suggesting(I am a forgetful mom sometimes). Now that my son is older, we do talk about what comes out of his mouth because he understands hurt feelings. It is hard for a 3 yr. old to understand what that means. I might have to try the penny jar thing though. At 6 it is becoming more helpful to take privileges away. In fact, when we buy something new(V-Tech game, new toy, etc.)my husband always says, "hey, it's just one more thing to take away when they mess up." I still say talk to your grandma(they are wise)unless she was not such a good mom, and figure out what works best for your son's age. I know time out didn't work for my son at 3. He would just pick up the "naughty rug" and play with it. good luck, and I'm sure this is something you can get a handle on pretty easy.