Truly water proof, unlined. After reading other reviews, I ordered 2 sizes up so that I could wear layers underneath in case of unpredictable weather on our trip to Alaska this summer.  I usually wear a size medium with bust of 38" and waist of 32"  I probably could have just ordered 1 size up, but I wanted to be sure. I did end up layering with a down jacket over a fleece vest, then lastly, this rain jacket when the evening temperature dropped to mid 40's on our small-ship cruise.  The main zipper of this jacket did tend to get stuck quite a bit making me wish the fabric was a little stiffer.