R.F.
no specific age as others have noted. my son was 4 1/2, he seemed ready at about 1 1/2 but I was told he was too young and it would be me being trained not him at that age - I put it off as my day care was not willing to work with him at that young age either. when he was between 2 & 3 I was being asked why he wasn't potty trained yet (by this time he had lost interest in using the potty & would scream & fight if I tried to sit him on either the little one or the big one) so it was a loose/loose situation for me. I gently persuaded him and used a potty chart that eventually worked for us - he got a star every time he used the potty and at 15 stars he got a small gift (like a hot wheels car or something small like that) then the next gift was at 30 (new) stars then the last one at 45 (new) stars. by then he was expected to go on the potty and no longer in diapers so no need for add'l gifts.