We put Haydn into a big bed at around 15 or so months I reackon, it was as soon as we realised he was climbing out of his cot, we thought then was a good idea. We put his mattress on the floor to start with and left the cot in the room as well, so we gave him the option of which bed he wonted to sleep in. He always choose the mattress on the floor. The first couple of times his room got trashed, I think it was a novelty that he had freedom, not that he already had that since he could climb out of his cot! So everything got taken out of his room that he could get to, including all creams etc! Not a easy thing to get out of carpets! Eventually we took the cot down and he wasn't worried, and eventually put the mattress on the frame, which was a big step, but we thought he was ready. We didn't put a rail on his bed though, and we have never had a problem with him falling out of bed either. I think we just shoved a few pillows under the mattress so he would roll towards the wall and not the floor. And now, the bed is no more of a novelty, but somewhere to sleep. Though at the moment he doesn't sleep in it, that is another story! I will admit I love having him come into my room and say "goodmorning mummy" in his cheerful voice and getting a wet kiss, it makes it all worth it. How can you get grumpy with that, you can't.