Police say there were around a dozen arrests at the Wellington Cup race day at Trentham in Upper Hutt, down 50% on last year.
The region's police were bracing themselves for what they described as their busiest day of the year with the races attracting around 25,000 people and a large crowd at an AC/DC rock concert in Wellington city.
Upper Hutt area commander, Inspector Mike Hill, says the big day at the races ran smoothly.
Organisers of the race day at believe their hard-line stance on alcohol is working.
Organising group RACE has banned BYO alcohol at the racing carnival for the last four years. It recently widened its policy to include major race meetings at all its tracks across the lower North Island, including Awapuni and Otaki.
Chief executive Matt Reid says 15 security guards were checking bags and chilly bins but very few people were attempting to smuggle in alcohol.
In 2006, before the ban was introduced, 50 people were arrested at the event.
Meanwhile, nine people were arrested at the AC/DC concert at the Westpac Trust stadium and six were ejected from the venue.
In all, police arrested 50 people in Wellington on Saturday night, up from the usual 30 or 40.