1. A comparison of direct measurement and M-mode echocardiography in the determination of posterior left ventricular wall thickness was performed in 26 subjects, of whom 21 underwent cardiac bypass surgery; the remainder came to necropsy.
2. In the surgical group a close correlation was demonstrated between direct measurement of posterior wall thickness and the echocardiographic end-diastolic dimension (r = 0·76, P < 0·001).
3. The necropsy measurement of posterior wall thickness correlated with the echocardiographic end-systolic dimension (r = 0·99, P < 0·001).
4. These findings confirm that the echocardiographic measurement of posterior wall thickness accurately reflects the anatomical dimension.