The present study was designed to assess the left ventricular (LV) function by the fractional shortening (FS)/end-systolic stress (ESS) relation in untreated hypertensive patients. METHODS Two patient groups were examined: group 1 was made up of 50 patients with essential mild hypertension (44 +/- 14 years) and group 2 consisted of 16 normotensives (35 +/- 12 years). LV mass, endocardial FS, mid-wall FS and meridional ESS were measured according to the classic formulas, as well as the 24-hour ambulatory blood pressure (ABP). FS/ESS relation was analysed in hypertensive patients by 2 different ways: 1 degree graphically, with the 95% confidence interval of the normal FS/ESS relation as a reference: 2 degrees statistically, by comparing the observed FS values with those FS value expected from ESS, using equations derived from normal subjects (McMemar chi 2 test, or binomial rule). RESULTS The graphic examination allowed for the identification of a depressed, normal or increased LV function in, respectively, 7, 31 and 12 patients, using the endocardial FS/ESS relation, against 30, 18 and 2 patients, using the mid-wall FS/ESS relation. Likewise, the statistical analysis of the differences between the observed FS values and the expected FS values showed 13 discrepancies, all of them being related to an overestimation of the LV function, an assessed by the endocardial FS/ESS relation (p < 0.01). Such a trend turned out to be more significant in patients with an increased ABP (n = 31; p < 0.05) than in "white coat" hypertensives (n = 9; p < 0.08): in contrast, it was of the same extent in patients with an increased LV mass (n = 17; p < 0.05) as in those with a normal LV mass (n = 33; p < 0.05). CONCLUSIONS 1/After adjustment for ESS, mid-wall FS (a direct measure of myocardial fiber shortening) was more often decreased than endocardial FS (reflecting chamber dynamics). 2/Mid-wall FS was also found to be a better tool for assessing LV function in patients with normal LV mass, and, to a lesser extent, in "white coat" hypertensives.