OT: Help! How can I get my 4 yr old to stay dry at night??

Thank you guys all so much for the ideas and experience... My hubby has been more worried about it than me, and it's stressed me out... There was a point where he went weeks at a time between having nighttime accidents, so I think that's where the concern mostly stemmed from. He's only four, and never has daytime accidents, so I won't worry too much about it for now.   :-)