I can't believe all these answers which are just guesses (and wrong ones) from people who haven't tried it. I tried it (yes, really, at least one of us did!) It isn't a hair dye - it contains some light-sensitive chemical (silver nitrate, I believe) which supposedly gets into your hair and darkens it gradually, over a period. In fact I tried it for a few months and there was little sign of any change, except that my powers of concentration were impaired, and I gave it up to preserve my last shread of sanity and changed to proper women's dye. Even Just For Men is no good. It's just like the women's version except that you don't get as much (our hair is supposed to be shorter), it costs more, and you get a slightly larger pair of disposable gloves. Men, take it from me, there are no half measures. L'Or�al Excellence Cr�me is the dog's ********.