There has been little research done on the differences between hyperthyroidie patients who exhibit cardiothyrosis and those who do not. The objective of this research was to elucidate the variations in echocardiographic parameters that exist between these two groups, in order to determine practical implications. A prospective study on 37 subjects was performed: 20 in group I (without cardiothyreosis) and 17 in group II (exhibiting cardiothyreosis). In both groups, women were predominant. Left ventricular diameters and volumes were statistically higher in group II (p < 0.0007). The left ventricular end systölic stress was also higher (140.10(3) +/- 37 vs 131.10(3) +/- 51 dynes/cm2. p < 0.05). There was no significance between the two groups in shortening fraction, ejection fraction and mean rate of circumferential fiber shortening. The E/A ratio of the mitral flow was higher in group II (1.98 +/- 1.3 vs 1.3 +/- 0.7, p < 0.05), but the isovolumetric relaxation time and the deceleration time of the E wave were similar in both groups. Left ventricular systolic dysfunction was observed in 5 patients of each group. Relaxation abnormalities were found in 10% of the subjects in group 1 and 33.3% in group II. Significant valvular regurgitation was observed only in group II (8 cases of mitral, 1 case of tricuspid and I case of aortic regurgitation). Given that cardiovascular perturbations may be different during the stages of the hyperthyroidism, different therapeutic approaches may thus be considered, facilated by appropriate echocardiographic examination.