I should probably have given a little more information. These are Tumbling Tom Tomatoes. I'm growing them in pots. I transplanted them from the little seedling containers into styrofoam cups about two weeks ago. Then about a week ago, put them into their current pot where they'll stay. The curling of the leaves started after putting them into the styrofoam cups.

Hi tuesday ;)- It is called "leaf roll" and is a normal response of the plant to any stress like transplanting, too much nitrogen fertilizer, too rapid top growth, too much water, high temps, etc. It doesn't affect production and can usually be ignored but it helps to ID the stress problem and eliminate it if possible. The plant will usually recover on its own. You can learn more about it it you search here on leaf roll or Google it for even more info. Enjoy your tomatoes. ;)

Dave