Get some 'ant stations' from your local DIY store or supermarket, and place them where the ants are worst, if they're bothering you, that is. Otherwise, leave them alone...

As Spritzh. says unless they are causing you a problem leave them be.

Have to agree with others. My gravel borders are infested with ants and at first it annoyed me because they're crawling all over the plants but now I've learnt they keep greenfly and aphids at bay...so leave them be :o)
If they really bug you then do as I did - carefully sprinkle some ant powder along the border (avoiding plants). Best to find where they're actually coming from or they'll be back again in a few days (like mine!)

I only use an ant station if they're the red ones which bite me when I'm kneeling down weeding or edging....they tend to make ant hills in the edges of the lawn or under a plant, which i have to deal with. I don't want my dog bitten by them either.