Mobile casualty units to help deal with the problem of drunk and injured revellers during the party season have been described as a "huge success".
A treatment room was opened at the Millennium Stadium
Field-style hospitals were set up in Cardiff and Swansea for Black Friday - one of the busiest nights of the year, as many businesses shut for Christmas.
Cardiff's temporary unit dealt with 15 patients, and Swansea's treated 12.
Police and medical staff said the operation had gone very well.
Under the scheme, rapid response paramedics deal with 999 calls from the pub and club areas of both Cardiff and Swansea, which left ambulances free for serious incidents.
Mark Winter, regional ambulance officer with the Welsh Ambulance Service, said staff were pleased with the outcome.
"It's gone very well, though it was a difficult one to try to organise," he said. "We have learned from this."
Those with minor injuries were treated at the temporary medical centres rather
than being taken to hospital accident and emergency departments.
The units will be set up again on Christmas Eve and New Year's Eve.
The initiative has come as the UK Government launched a national crackdown on binge drinking.
From Friday, police were given the power to issue on-the-spot fines for buying or selling alcohol to under-18s. The penalty for drunk and disorderly behaviour was also increased from £50 to £80.
Staff were pleased with the way things went
Police from more than 180 areas across England and Wales will have the power
to issue the fines until 3 January.
South Wales Police said 22 people were arrested in Cardiff city centre on Friday night and during the early hourse of Saturday. In Swansea, 19 arrests were made.
Cardiff normally welcomes up to 50,000 people on a normal Friday night.
Sergeant Mike Davies said the arrests made were for public order offences, including criminal damage, being drunk and disorderly and assault.
He said officers did not issue on-the-spot fines. Offenders were be arrested and taken to the custody suite at the police station, and might be issued fixed penalty fine there.
Inspector Tony Bishop added: "There were a few more people around than normal, and a few office parties carried on into the night.
"There were more people out and about but generally they were law-abiding individuals - a run-of-the-mill Friday night."