Auckland Hospital's emergency department had its busiest ever day during the holiday period, and the second busiest month of last year.
In December, the department treated 4036 cases second only to October's 4075.
New Year's Day was the department's busiest day ever.
Tim Parke, a clinical manager at the hospital, says cases involving alcohol were noticeable during the holidays.
Dr Parke says the department also has significant concerns about the unregulated use of quad bikes.
The emergency department's research unit is investigating quad bike related deaths and injuries, he says.