I agree with the previous poster, every time you run Romba, you have to empty out the dirt compartment, take the beater brushes off and pull the hair, lint and thread off the brushes (if you use a cat or dog brush this works fantastically) and remove the lint that's wrapped around the ends of the beater brushes. Every other time, you need to remove the thread and hair wrapped around the rotating brush (sometimes you need to remove the Phillips head screw holding this on and really clean it out). Finally the rolling ball wheel needs to be popped out using a narrow, small screwdriver and all the stuff trapped in there removed.

Needs a good cleaning.