I agree with Patricia's post...just ride out the phase and cuddle him when he's feeling clingy as you reassure him. When dropping him off someplace, just remind him that you will be back as you always come back for him and he can do fun things and tell you about it when you come back. We have 2 boys who just turned 3.5 and 2. For quite a while, the 2 year old was a Mommy's boy and the 3.5 year old was a Daddy's boy and that's who they would cling to if feeling clingy or given the choice of who to go to. Lately, the 3.5 year old is all about Mommy wanting Mommy to get him what he wants, wanting Mommy to put him to bed, etc. The 2 year old has been keeping a close eye on Daddy, wanting Daddy to hold and cuddle him more and wanting Daddy to put him to bed, so they did a little role reversal lately. Every once in a while the 3.5 year old has gotten clingy as you describe, though he hasn't cried when we left him for quite a while now. He'll tell me he doesn't want to go to the child center at the gym sometimes, but then he goes in and plays fine while there and has fun. It's just for a short time that he clings and then he's back to normal for a while until the next clingy phase, and it's definitely lessened a lot as he gets older. The 2 year old still cries EVERY time we leave him, though it is lessening little by little. He's strong willed, so he's more intense about wanting to be held, who he wants to hold him, etc., but he's getting there. Seems like your son is simply working now to establish those roots of feeling secure. :)