OBJECTIVE Color kinesis (CK) is a real-time echocardiographic technique based on acoustic quantification that yields regional and global information by tracking and color-encoding endocardial motion. The aim of this study was to determine the feasibility and usefulness of diastolic CK images with ICK software to objectively assess global and regional left ventricular (LV) diastolic function. Accordingly, diastolic properties obtained from CK images were compared with conventional Doppler echocardiographic indices. METHODS We studied 56 subjects who underwent echocardiographic evaluation in our laboratory for assessment of cardiac structure and function. Criteria for inclusion included the presence of normal sinus rhythm and adequate two-dimensional echocardiographic imaging. Exclusion criteria were (1) all types of arrhythmias, (2) pericardial effusion, (3) heart rates <55 or >90 beats/min, (4) abnormal interventricular septal motion caused by right ventricular pressure or volume overload, (5) moderate to severe mitral or aortic regurgitation, and (6) mitral valve stenosis. Using pulsed Doppler echocardiography, peak velocities during rapid filling (E) and atrial contraction (A) were measured, and the E/A ratio and deceleration time of the E wave velocity (DT) were calculated. The time-velocity integral (TVI) of the E wave (TVI-R), A wave (TVI-A), and rapid-filling fraction (TVI-R/TVI-R+TVI-A) was measured. The early diastolic mitral annular velocity (Ea) was measured by tissue Doppler. The 56 subjects were divided into the following three groups: (1) an impaired relaxation group consisting of 30 patients with normal ejection fraction and a mitral inflow pattern with a reduced E/A ratio (E/A < 1.0); (2) a pseudonormal group consisting of 18 patients with a mitral inflow pattern with an increased E/A ratio (E/A > 1.0), an increased E/Ea ratio (E/Ea 10), and no shortened DT (≧140 ms) [patients with hypertrophic cardiomyopathy (HCM, n = 8), dilated cardiomyopathy (DCM, n = 8), and aortic valve stenosis (n = 2) were included in this group); and (3) a restrictive group consisting of eight patients with a mitral inflow pattern with an increased E/A ratio (E/A >1.5), an increased E/Ea ratio (E/Ea ≧10), and a shortened DT (<140 ms) [patients with DCM (n = 5) and HCM (n = 3) were included in this group]. As a control group, 20 normal subjects (30 ± 18 years) were selected on the basis of having high-quality echocardiographic images. Diastolic CK images were obtained from the LV midpapillary short-axis view. The analysis of CK diastolic images was performed by using ICK software. The CK-diastolic index (CK-DI) was defined as the degree of LV segmental expansion during the first 30% of diastole, expressed as a percentage. The mean CK-DI was calculated from the average CK-DI of six LV segments. RESULTS No relationship was observed between mean CK-DI and rapid-filling fraction in any of the study subjects (r = -0.092, P > 0.2). Mean CK-DI was significantly lower in the restrictive group (34.2% ± 4.3%) compared with the normal group (70.6% ± 7.4%), the impaired relaxation group (50.5% ± 7.7%), and the pseudonormal group (42.3% ± 7.5%). The reduction of mean CK-DI was found to be associated with the progression of LV diastolic dysfunction. CONCLUSIONS We conclude that the analysis of diastolic CK by using ICK software is a useful technique that can be applied to quantitative evaluation of LV global diastolic function.