To document the risk of road accidents associated with minimal visual acuity (equal to 6/12 or 6/15) and lack of binocularity (stereoacuity > or = 200 sec arc), 1400 drivers who had had an accident during their 70th year were compared with 2636 controls randomly selected from the 30,000 70-year-old drivers who had had no accident during the same time. Information on visual characteristics and demerit points was obtained for all subjects from the Quebec Automobile Insurance Board. Mileage and prevailing driving conditions were documented through a mail questionnaire. The relative risks of accidents were estimated while controlling for traffic convictions, mileage, time spent and frequency of driving during rush hours. Drivers with minimal visual acuity alone had the same risk of road accidents as other drivers (OR = 0.97 CI 95%: 0.68-1.38). The risk of accidents among drivers with both minimal visual acuity and lack of binocularity was moderately higher than among other drivers (OR = 1.23, CI 95%: 0.88-1.72).