For a dedicated admirer of the feline species, not many things are sweeter than a furry cat circling and rubbing up against your legs. Thankfully, these actions are no cause for alarm. No action is necessary on your part, apart from a gentle stroke of your kitty's back, perhaps.
Rubbing Up Against You
If your precious fluff ball is circling your legs and rubbing her body against them, she is engaging in a classic territorial feline behavior. Essentially, she's marking you with her own individual smell and communicating to the rest of the world -- especially to other cats -- that you are her property, and her property alone. Yikes! Although the action is indeed sweet, remember that she is claiming you to prevent others from doing the same thing.
Since human beings can't exactly mark their turf by rubbing up against things, the concept may be difficult to grasp. However, cats possess scent glands throughout their bodies, from their paw pads to their foreheads. When your cat rubs up against you using her cheeks or her forehead, she emits pheromones that serve as chemical messages to others. Although it may seem like a simple loving gesture, it's actually much more than that.
When your cat circles and rubs up against you, it isn't always strictly an ownership thing. It also may just be a kitty request for a little bit of attention in the form of cuddles and strokes. If your cat is circling you and rubbing up against you, what you can do is reward her effort by engaging her in a petting session.
Rubbing Up Against Items
Although circling is a classic feline way of maneuvering in and out of your leg area to leave her mark, you may notice that your cat also does this with other things, particularly doors. When a cat is feeling territorial and wants to claim her turf, it is in no way restricted to humans. You may observe your cat rubbing up against her favorite toys, living room furniture and even food bowls. All of this is completely typical cat behavior. No need for immediate action or to contact the veterinarian, either.