This study examines the association of isolated systolic hypertension with left ventricular (LV) mass and geometry in men and women. The subjects of this study were surviving members of the Framingham Heart Study and the Framingham Offspring Study who attended the index examination (between 1979 and 1983) and were aged ≥50 years, free of clinically apparent cardiovascular disease, not taking antihypertensive medication and without diastolic hypertension (diastolic blood pressure <90 mm Hg), and in whom LV mass could be determined by echocardiography. Examinations routinely included 12-lead resting electrocardiography, measurements of resting blood pressure, anthropometry, blood glucose levels, and M-mode echocardiography. M-mode echocardiograms adequate to assess LV hypertrophy were obtained for 1,282 normotensive subjects (538 men and 744 women) and 79 subjects with isolated systolic hypertension (26 men and 53 women). Adjusting for age, body mass index and diastolic Mood pressure, the relative odds of LV hypertrophy associated with isolated systolic hypertension were 2.58 (95% confidence interval 0.97 to 6.86) in men and 5.94 (95% confidence interval 3.06 to 11.53) in women. Women with isolated systolic hypertension had increased LV wall thickness and mass without LV chamber enlargement, but men had LV dilation and increased LV mass without increased wall thickness. In conclusion, although isolated systolic hypertension was associated with increased LV mass in men and women, the geometric pattern of increased LV mass differed by sex; although women demonstrated a pattern of concentric hypertrophy, an eccentric pattern was observed in men.