Parents of children with functional constipation often report that their child will urinate in the toilet with no problem but will only defecate if they are wearing underwear or are in a diaper or Pull-up. Why is this? Understandably, parents think that if their child is relaxed enough to pee in the toilet he or she should also be relaxed enough to poop in the toilet. However, as I explain in the 2nd edition my book The Ins and Outs of Poop: A Guide to Treating Childhood Constipation, the fear that underlies functional constipation is related to relaxing the anal sphincter (not the urinary sphincter!) whenever a child consciously or subconsciously feels the need to poop. Most of the children who pee in the toilet but do not poop in the toilet are still actively withholding and frequently have poop "accidents" in their underwear or diapers (See Chapter 9). In my book I explain why withholding must be treated and stopped before the application of "successive approximation" behavioral strategies can enable these children to poop on the toilet without fear ( See Chapter 16).