Mass street parties across Spain in response to high bar prices have led to clashes with police, leaving 80 people injured and at least 50 arrested.
Firefighters were called out to 50 blazes in Barcelona
The most serious violence was in Barcelona, where police used batons and rubber bullets and youths set fire to rubbish bins in the street.
There were street battles on a smaller scale in the university town of Salamanca, north-west of Madrid.
The government and parents' groups appealed to young people to stay away.
Teenagers across the country used internet chat rooms and text messaging to plan their drink-out at "macrobotellon" (big bottle) parties.
The parties have become a tradition in recent years among teenagers because of high bar prices.
Street parties were held in some 20 cities in all on Friday, including Madrid.
The highest attendance was in Granada, where around 25,000 young Spaniards gathered.
Spain is known for its party spirit but authorities frown on botellones
But in Barcelona 68 people, including 37 police, were injured and dozens arrested after youths threw bottles and cans and held pitched battles with police in the narrow streets of the old city.
Firefighters were called out to 50 blazes in the city and shop windows were broken and looted.
A firefighter and five police were among the injured in Salamanca.
In the capital, revellers faced a 300-euro fine for drinking in the street under a ban introduced in 2002.
Seven other of Spain's 17 regions had also banned the binges, which critics say usually result in noise, fights and piles of rubbish.