Police arrested 50 people in Wellington on Saturday night as numbers in the city swelled following the AC/DC concert and the Wellington Cup race day.
Nine people were arrested at the concert itself at Westpac Trust stadium, and six were ejected from the venue.
Six ambulances were called to treat people with alcohol or drug-related issues.
Police say the usual number of arrests on a Saturday is between 30 and 40.
Meanwhile, Auckland police were kept busy with complaints about general disorder on Saturday night, including a wedding in Te Atatu where about 15 people exchanged blows.
A police spokesperson says there were a number of brawls and that they attended numerous functions where fights had broken out and alcohol was involved.