Little more info? Are there spots on your leaves? Tiny black specs on the undersides of your leaves? If so this could be mites. Mites also lay eggs, which look like white specs on the underside along the veins of the leaves.
Caterpillars like to chew, so if you have holes in your leaves, this could be the problem.
How far are you into your grow? If you're still in veg, there are a lot of preventative/eradication methods you can use. If you're flowering, these choices become limited. More info would help on this subject, as well as pics. If in veg still, I highly recommend Neem oil for preventative measures. Like massah suggested, no-pest strips are effective and are a good eradication method.
Good luck and hopefully you can provide some more information to get some better answers!
FattyCaps