A new prediction model estimates the 3-year rupture risk for saccular cerebral aneurysms and could aid clinical decision-making. Using data from 5,651 Japanese patients, researchers built a simple scoring system that uses easily available patient and aneurysm information. The best predictors of 3-year rupture risk were older age, female sex, and hypertension. Aneurysms that had diameters >20 mm, had daughter sacs or were located in the communicating arteries were particularly likely to rupture. The prediction model has not yet been tested in non-Japanese individuals.