The usual electrocardiographic criteria recommended for left ventricular (LV) hypertrophy may be unreliable in the presence of complete right bundle branch block (BBB). Thirty-six standard electrocardiographic criteria for LV hypertrophy were evaluated in 100 patients (mean age +/- standard deviation 67 +/- 11 years) with right BBB and technically satisfactory echocardiograms. Eight additional electrocardiographic criteria derived from this study also were evaluated. LV mass index was determined from the echocardiogram using the Penn method. LV hypertrophy defined as LV mass index greater than 132 g/m2 in men and 109 g/m2 in women was present in 56 of the 100 patients. Electrocardiographic criteria with the highest sensitivity were SIII + (R + S) maximal precordial lead greater than or equal to 30 mm (sensitivity 68%), specificity 66%), left axis deviation of -30 degrees to -90 degrees (sensitivity 59%, specificity 71%) and combination of left axis deviation and SIII + (R + S) maximal precordial lead greater than or equal to 30 mm (sensitivity 52%, specificity 84%). The electrocardiographic criteria with the highest sensitivity and specificity greater than 90% were left axis deviation of -30 degrees to -90 degrees and SV1 greater than 2 mm (sensitivity 34%), point-score system, RaVL greater than 12 mm and RI + SIII greater than 25 mm (each with a sensitivity of 27%). In general, limb lead voltage criteria such as RaVL greater than 11 mm (sensitivity 29%, specificity 86%) had higher sensitivities than criteria using right precordial lead S-wave voltage criteria such as SV1 + RV5, V6 greater than 35 mm (sensitivity 2%, specificity 100%).(ABSTRACT TRUNCATED AT 250 WORDS)