Doctors have developed a simple checklist to show if patients who have had a mini-stroke are at immediate risk of a more serious attack.
Stroke can affect a person's ability to move limbs
The Oxford University team, writing in the Lancet, said it could help identify those needing emergency treatment.
It looks at age, blood pressure, symptoms and how long the mini-stroke, or transient ischemic attack, lasted.
UK guidelines say all such patients should be checked within seven days, but many wait at least two weeks.
The researchers say their guide could be used to help identify the 10% of patients who are at risk of having a major stroke within seven days of a mini-stroke.
Giving this group blood-thinning drugs or other treatments to reduce their blood pressure or cholesterol can cut their risk of further attacks.
Transient ischemic attacks (TIAs) occur when bloodflow to the brain is temporarily blocked.
This can cause eyesight or brain problems. However, unlike full strokes, these symptoms disappear within 24 hours.
'No more funding needed'
The researchers first looked at data on around 200 patients taking part in the Oxford Community Stroke Project, who had experienced a TIA, to see who had gone on to have another stroke within a week and what symptoms they had initially displayed.
Based on this information, the researchers developed a points system in which being over 60, having raised blood pressure, a weakness on one side of the body or speech disturbance were all linked to increased risk.
The researchers then tested the ABCD check (age, blood pressure, clinical symptoms and duration of TIA) on a further 400 patients who had experienced a mini-stroke.
The risk of stroke within seven days of TIA was over 30% in patients with a high ABCD score, whereas there were no early strokes in patients with low scores.
Professor Peter Rothwell, who led the study, told the BBC News website: "It's a question of working out which individuals need to be seen on the day, or as soon as possible, and who is at low risk and can wait to be seen at the weekly clinics.
"This check is not complicated science - this is a very simple observational risk score."
He added: "Current guidelines on the urgency with which TIA patients are investigated need to be revised.
"These improvements would not require an increase in funding and could be achieved simply by more effective use of existing resources, however, changes in health service policy would be needed for this to be achieved."
Appropriate treatment call
Joe Korner, of the UK's Stroke Association, which funded the research, said: "All too often, TIAs are ignored.
"But Professor Rothwell's work can help to predict whether someone who has had a TIA is going to have a catastrophic stroke that could be fatal or severely disabling."
He added: "It is essential that all TIAs are diagnosed quickly so that patients can be assessed and immediately started on the most appropriate course of treatment."
He called on the Department of Health to ensure all GPs and hospital staff were aware of the tool.