Police had to break up a crowd of 200 revellers during Australia Day festivities in Perth, while a young man was arrested after assaulting transit officers on a train.
But police said most Australia Day revellers were well behaved, particularly along the Swan River foreshore for the nation's largest fireworks display.
Police were called to Manners Hill Park in Peppermint Grove about 9.20pm (WST) where they found 200 youths creating a disturbance.
The group smashed bottles and yelled abuse at police, who managed to disperse the crowd an hour later without any arrests or injuries.
In a separate incident, an 18-year-old man allegedly assaulted two transit officers who were escorting him off a train at Kwinana station for carrying alcohol.
It is alleged the man assaulted both male officers about 9.20pm before he ran into bushland near the train station.
He was found by a police dog and charged with two counts of assaulting a public officer and one count of disorderly conduct.
Despite these incidents, Acting Assistant Commissioner Lawrence Panaia said it was an "almost incident-free" Skyworks event along the foreshore.
"Arrests were well down on last year and given the vast number of people attending the various all-day events, there were a relatively small number of incidents which required police action," he said.
Across WA, 101 people were arrested/summonsed and 145 move on notices were issued.
One person was charged with assault, 41 with disorderly behaviour and 78 with traffic infringements.
There were also 17 drug infringements, 27 liquor infringements, one person with an alcohol reading in excess of 0.05 per cent and one person in excess of 0.08 per cent.