Left ventricula wall thickness (LVWT) was measured by ultrasound in 100 subjects without heart disease. The data on both diastolic (LVWT,) and systolic (LVWT,) thickness were related to sex, age, weight, height, heart volume (HV), and ECG voltage criteria. LVWT, was greater in men (P<0.01) but LVWT, was of the same magnitude in both sexes. In both sexes LVWT, and LVWT, increased with age (P<0.001). In women LVWT, correlated with HV but not in men (R=0.429; P<0.001 for women, R=0.145; P>0.05 for men). This was caused by an increasing HV with age in women, in contrad to the steady HV in men. There was no carelation between LVWT, and weight in either sex. LVWT, and height was not related io men but in women there was an inverse correlation between LVWT, and height (R= -0.102:P>0.05 for men, R= -0.363:P<0.01 for women). No significant correlation was found between the LVWT and ECG voltage criteria. Irrespective of sex and age the upper normal limit for LVWT, was 12 mm and for LVWT, 18 mm.