The incidence, average number, and localization of lesions of the white matter detected by the T2-weighted nuclear magnetic resonance images among volunteers without cerebrovascular symptoms have been correlated with the number of risk factors for stroke. Accepted risk factors were arterial hypertension, diabetes mellitus, smoking, hypercholesterolemia, and cardiac disease. The 42 subjects examined were divided into Group A (0-1 risk factor, mean age 59.36 +/- 5.73 years), Group B (2 risk factors, mean age 61.54 +/- 8.33 years), and Group C (greater than or equal to 3 risk factors, mean age 62.57 +/- 9.83 years). Multiple risk factors among the age-matched groups was accompanied by a highly significant increase (p less than 0.001, Group A versus Group B; p less than 0.01, Group A versus Group C) of the incidence of white matter lesions. The average number of white matter lesions was increased (p less than 0.001) when Group A was compared with Groups B and C. Ninety-two percent of the white matter lesions were localized in watershed zones. Only 11 of the 155 abnormalities of the white matter detected by nuclear magnetic resonance imaging could be detected by computed tomography. White matter lesions in T2-weighted images appear to be an early stage of cerebrovascular disease.