Dunedin Police are looking at throwing the book at those caught up in the major disturbance in the university campus area over the weekend.
69 people were arrested for disordely behaviour but 21 of them have had their charges upgraded to the more serious crime of rioting.
Canterbury University's annual Undie 500 motor run to Dunedin lead to street partying that descended into couch burnings, bottles thrown at Police and firefighters and more than $12,000 in damage to emergency equipment.
As police comb through video footage to see if any other charges can be laid the first of those charged will start appearing in Dunedin's district court on Friday.