For most children it will be sometime between their second and third birthday. Some are ready earlier than others, and some are more enthusiastic than others. You should give it a go when you think your child might be ready, i.e. interested in using the potty, but if there is no success then putting it off for a while might be better. Keeping positive about it all is probably the most important thing, for if your child becomes negative it could turn into a battle. Girls are often ready to be trained earlier than boys because they have better bladder control at a younger age. And most children will not master the art of bladder control at night until much later.