Using multigated radionuclide ventriculography (RNV), the left ventricular (LV) phase histogram (PH) was used to quantitate LV synchrony at rest and at submaximal and maximal supine exercise in 10 normal and 10 coronary (CAD) patients. Each LV PH was obtained by masking the phase image with an LV region, generated semiautomatically and modified if necessary to minimize ambiguity of LV delineation. The shape and spread of each histogram was characterized by its standard deviation (SD) and skewness (SK). Normals had a tight resting PH with slight negative skewness (SD = 9.06 +/- 0.22 (mean +/- SEM; SK = -0.53 +/- 0.05). CAD patients had a wider resting PH with a larger SD and a significantly more positive skewness reflecting greater contractile asynchrony (SD = 16.53 +/- 2.26; SK = 0.35 +/- 0.22). With exercise the PH distribution for the normals remained tight (SD = 8.1 +/- 0.24) while SK changed little (SK = -0.29 +/- 0.04). In contradistinction, with exercise CAD patients markedly increased the spread of their LV PH (SD = 27.42 +/- 3.77) and increased the number of late pixels (SK = 0.75 +/- 0.15). It is concluded that quantitative PH analysis is a useful adjunct for the analysis of regional asynergy during resting or exercise radionuclide left ventriculography.