Vietnam has banned the sale and possession of hamsters, whose popularity has been soaring.
Hamsters are one of many items imported illegally
The Ministry of Agriculture says anyone caught with a hamster will be fined up to 30m dong ($1,900) - almost double the average annual wage in Vietnam.
The authorities say the creatures are a potential source of disease.
Officials have also expressed concern that the animals are imported from China and Thailand without proper licensing or controls.
In a tropical Asian country like Vietnam, hamsters are not a traditional pet of choice.
That role has normally been held by various types of fish.
But a combination of factors including growing incomes and the Chinese Year of the Rat have made the beady-eyed rodents highly desirable.
They have been trading for $10 to $20 each and are reported to be a hit with the young population of Hanoi and Ho Chi Minh City, spawning a whole sub-culture of hamster forums and hamster clubs.
But the authorities are concerned.
Traded illegally from China or Thailand, the hamsters are unlicensed and unchecked.
The Ministry of Agriculture has highlighted the risk of disease.
The animals are just one of many imports that escape adequate scrutiny or epidemiological control in Vietnam.
A recent survey alarmingly showed that most anti-malaria drugs - in Vietnam and other countries of the region - were fakes traced back to China.
And reports abound of other counterfeit or dangerous items sold for human consumption - including rather startling internet rumours of a trade in fake chicken's eggs.