Forty-one people were detained overnight in Letterkenny garda station following Day 2 of the Donegal International Rally.
The arrests were for a series of public order, drug and driving offences.
Gardaí say they had an extremely busy night following Day 2 of the Rally.
Between 5pm yesterday evening and 7am today, there were 41 people in custody at Letterkenny garda station.
There were 21 arrests for public order offences, one for an assault causing harm and one for an assault on a garda.
Eight people were also arrested for a search under the Misuse of Drugs Act and one over the sale and supply of drugs.
In relation to driving offences, four arrests were made for dangerous driving, one for being drunk in charge and four for drink-driving.
Gardaí have renewed their appeals for people attending the rally today to drive carefully and to have regard for others using the roads.