The remedy is used by many to treat complaints including depression
People with epilepsy should be warned that using a popular herbal remedy may increase the risk of seizures, researchers say.
German scientists, writing in the Journal of Natural Products, said they had found 10 written reports of seizures linked to ginkgo biloba.
They said they were convinced the herb could have a "detrimental effect".
A leading UK epilepsy charity said the evidence was not yet compelling, although it said care was needed.
Ginkgo biloba remedies - made from the leaves of the tree of the same name - is used by many thousands of people in the UK as a remedy for health problems ranging from depression and memory loss, to headaches and dizziness.
The team from the University of Bonn focused on a particular chemical compound in the herb called ginkgotoxin.
They said that evidence suggested that it might alter a chemical-signalling pathway in the body linked to epileptic seizures, and potentially interfere with the effectiveness of anti-seizure medications.
In addition to any benefits, which still remained unproven, they wrote, there was a "clear potential for adverse effects", particularly in susceptible patients
Even though there was no definitive proof that the herb had been the cause of the increase in seizures in the reported cases, patients should be warned about the possibility, and manufacturers asked to test their ginkgo products for levels of the toxin.
Professor John Duncan, from the National Society for Epilepsy, said that the current evidence did not necessarily warrant restrictions on the use of the remedy.
He said: "We believe that some herbs, for example St John's wort, are linked to a higher risk of seizures, but there is still not a great deal of evidence about problems related to ginkgo.
"We would say that if someone who has epilepsy wants to take this remedy, they should simply be aware of the possibility."