Heroin worth an estimated £25,000 has been seized by officers following a car chase, police said.
A Ford Fiesta was pursued and stopped by police in the Redburn area near Dumbarton on Saturday evening, and the Class-A drug was discovered.
Police Scotland officers have arrested and charged a 21-year-old man in connection with the discovery, and he is expected to appear at Dumbarton Sheriff Court on Monday.
Sergeant Kevin Craig, from the Argyll and West Dunbartonshire Road Policing Team, said: "Drug misuse brings nothing but misery to our communities.
"I want to reassure the people of Argyll and West Dunbartonshire that we will use every tool and tactic at our disposal to remove these illegal substances from the region.
"Our work often relies on the support of the public and together we can all make a difference and reduce the threat of such criminality.
"If you have any information or concerns about drug misuse, do not hesitate to contact Police Scotland on 101 or report this anonymously via Crimestoppers on 0800 555 111."