Thanks so much to the reviews on Amazon, I bought this product for mildew behind the clear caulk on our cultured marble shower. It worked! It took three applications to get rid of all of it, with no scrubbing whatsoever! It smells loud and must be thoroughly ventilated, but that was no problem. The shower looks new again! I am more careful now to dry off the caulk after every shower, and I will never be without this stuff!