This is a good time to try to get rid of the bottle. There are a few different ways to do it, depending on how many bottles he's taking a day, how attached he is to them, and his temperment. If your son is still taking three or four eight ounce bottles a day, it would be very hard to just stop suddenly. I would recommend that you get rid of one bottle (the one he's least interested in) and then wait four or five days before getting rid of the next one. Keep dropping out one bottle every four or five days until you are finished. The last bottle (usually the one before going to bed) is often the most difficult to stop, and you may have to help him learn another way to settle down before bedtime (this is a great time to begin a bedtime routine of reading a story). While you are cutting back the bottles, you should give him milk in a cup at his meals and snacks.

If he's only drinking one bottle a day, you may be able to just stop it, without much of a fuss. If you think it will be a difficult thing to give up, you could try the gradual method with the one bottle. In other words, if you normally put eight ounces in the bottle, try putting in six for a few days, then four, then two, and then stop all together.