My advice is simple. Pick a long weekend and stay home. It will be boring and you'll want to pull your hair out but it works. Ditch the diapers and pull-ups completely and have him be in underwear. Set a timer for every 20 minutes and sit him on the potty. He'll have accidents but after 3 days of doing this non stop he'll get it. Also, never ever use pull-ups again. If he can pee and poop in them, they're a diaper.

I agree with Barbara to back off and don't talk about it. My son was still 3.5 and hadn't been trained. I tried all the reinforcements under the sun and it didn't help. I did, however, ditch the diapers and only used pull ups during the overnight. I just waited him out and just when I thought he was never going to be trained, he all of a sudden became potty trained in about two days. It also helped that he was in daycare and had "peer pressure" to use the toilet. You will have to put up with accidents, but eventually he will not like being wet or messy and will start using the toilet. Night time and bowel movements may take longer, so don't worry. Good luck!:)

Our Daughter had a bed wetting problem until middle school.
My Dad (God rest his soul) heard of our dilemma, he told us his story, he wet the bed until he was 12, his Dad beat him regularly.

He gave us advice that worked, don't be upset, in time this too will pass, just don't make a big deal of the problem.

My addition is
Always have a discrete supply of pullups on hand.

I have two boys both with winter birthdays. I trained both of them the summer after their 3rd birthday. My older son trained in one week. Nights, poops everything. My younger son took months and months and months. He wasn't ready. I knew he wasn't but my husband was adamant that we train him the way we did our other son. Big mistake. It was incredibly frustrating and he still wears pull-ups at night. Don't train him until he's ready. It will cause nothing but frustration and tears for you both. I wish I'd waited with my younger son.

If a 31/2 year old cannot do all 7 of those things, then I'd suggest that he/she has learning disabilities. And, frankly, there are MANY children who are completely (daytime) potty trained at 2 or 21/2 yrs old. And that's in this country - in other countries with other norms, children toilet train much earlier. What I know from 20+ years in the early childhood education field is that some children need a much stronger push - and that also at 31/2 yrs old children also know that's it's easier to stay in diapers if they don't get that strong encouragement. And that (unless there are learning disabilities or physical disabilities precluding it) children don't go to kindergarten in diapers. so you can either not push at all and just wait for a year or so for him to have a eureka moment or you can do what the other poster suggested: spend a long weekend in underwear and then forever in underwear (except at bedtime) and go cold turkey. do not be punitive, but be matter of fact: it's time for you to be in underpants. Frankly, if you do the wait until a eureka moment, I actually think that he will still get a push or a shaming moment(s) but it will be from other children - a feeling of "why are you in diapers still, those are for babies" comment from a very confused 4 yr old who isn't trying to be mean. so do you want your child to be shamed by others? or do you want to do the "push" without shaming and do the cold turkey method?

I just have to say that being "completely" potty trained does not mean a child wears pull-ups or diapers to bed. Completely is completely. They're not completely trained until they wear underwear exclusively.