What Karrie said. As a lady of the boob I can wear exactly the same top as my flat chested sisters, and I will show cleavage where they won't. My breasts are there, not a lot I can do about them. Nor would I want to - I'd rather celebrate them than wear a high-necked t-shirt / jumper, which wouldn't really give me a 50s sweater-girl look, more a matronly monobreast. And while that may make you feel slightly more comfortable in a meeting than my showing an inch or so of cleavage, I'd rather not look shit, so tough titties. However, and I do think this is important, people should dress appropriately for the office. I've recently had to deal with this situation myself. Not specifically about cleavage - sometimes cleavage, sometimes skirts that barely cover the gusset, sometimes strappy dresses more suited to the beach showing expanses of skin, even flip flops. If your dress code is professional business wear then people should respect that and dress accordingly, and if she's really dressed inappropriately, rather than just showing a bit of cleavage, then something has to be said. That said, have you considered that the woman in question might not actually realise? I handled it with my team by addressing the whole team together (rather than just the 2 or 3 individuals concerned), and using the hot weather as an opportunity to reestablish the office dresscode. Job done.