potty training a 4 year old

I have a 4.5 year old boy.  He is my third child.  At 3 he went into underwear with interest in using the toilet but inconsistent success, perfectly acceptable and normal.  It took him about 6 months to master peeing on the toilet with accidents only when access to a bathroom was difficult and he really had to go.  It took about 15 months for him to master getting to the toilet for pooping, we crossed that hurdle this past summer.  Now that we are comfortable that he knows how to use the toilet, feels comfortable with a toilet and he knows when he has to go we are back to frequent urine accidents.  The two typical scenarios are:  1.  The pee starts and then he runs to the bathroom leaving enough pee in his clothes that he needs to change.  2.  He is holding/putting off pooping such that he can't hold the urine, too.  The first scenario obviously occurs when he is engrossed in something else, playing, a tv show, etc.  We have done rewards, punishments, charts, prizes, etc for 18 months - he just doesn't seem motivated, if we didn't say anything he could care less that his pants are wet.  He will be back at preschool next week - how do we get past this hurdle?  It is so frustrating and exhausting.  Help  :0

[Kevin Kennedy, Ph.D.]

At this point he is clearly ready to complete the toilet training process. Make some favored daily pursuit contingent on his using the bathroom. It's OK now to set firm limits on this.