Ambulance and medical personal are gearing up to look after people at the Big Day Out music festival in Auckland.
The 12-hour event is underway at Mt Smart Stadium and more than 40,000 people are expected to attend on Friday.
St John Ambulance says the concert is one of its busiest days and it has 150 staff on hand.
Events manager Charlotte Guscott says the most used items are likely to be vomit bags, paracetamol tablets, band aids, wound irrigation solution and cold packs of ice.
St John has set up a field hospital, two portable medical units and a series of first aid posts manned by volunteer doctors, nurses and paramedics.
The service was flat-out last year treating 1415 people. Fifteen had to be taken to hospital.
Ms Guscott says there is a new party drug on the market this year, which medical crews will be monitoring for when checking patients.