There were plenty of (ahem) four year olds on the slide to my eyes (if some of these kids were six days past three, it would be a wonder! However, no one was checking birth certificates at the top) - but it IS rather high and goes kind of fast. My four year old (really four and a half - 41" tall) took three days to work up the nerve to go down it - and she is the one who isn't shy about this sort of thing and had also worked up a lot of excitement about the Mickey Slide pre-trip - so maybe it won't even be an issue. Two flights of stairs up to the top kind of spooked her. They go down the slide all the time at our community pool into deep water, but there they go down in Mom's lap. (Once she went down she went down over and over and over and over......)