With the little experience I've had in the hair room, the best thing to do would be to go to each of the body parts in the Pose Room that the hair is likely to collide with (Head and Neck being the most obvious), and make sure that collision detection is turned on for them. Also, make sure collisions is set to on. Then head to the Hair Room, grow the hair you want, set its dynamics (can't help on this score, since I've only ever used the default settings), make sure 'do collisions' is checked, then calcualte dynamics. Hope this helps? Jon