Left intra ventricular filling was studied by colour M-mode Doppler ultrasound to determine whether the flow pattern can be assessed visually, and explore its relation to left ventricular (LV) function. Patients with coronary artery disease (CAD) or dilated cardiomyopathy (DCM) were divided into three groups according to angiographically evaluated LV function. The groups were compared with a control group of 54 healthy volunteers. The mitral to apical delay of early diastolic flow was qualitatively assessed from printed colour M-mode images, twice by four independent observers blinded to the subject's status. The repeatability of the assessments as determined by the kappa statistic was good intra observer (kappa = 0.75) and moderate inter observer (kappa = 0.53). The CAD-group with angiographically normal LV function (n = 25) had flow patterns resembling those observed in the control group. The group with ejection fraction (EF) < 50% (n = 19) had flow patterns clearly different from the control group. Patients with regional wall motion abnormality (RWMA) but EF > 50% (n = 16) exhibited flow patterns intermediate between the control and the low EF group. Among the 50 CAD patients there was a negative correlation between EF and the presence of delay of apical peak velocity (Spearman's rs = -0.62, p < 0.0001). A visible delay of apical peak velocity had a sensitivity towards DCM of 83% and specificity of 75%. The sensitivity towards CAD with either RWMA or low EF was 55% and the specificity 75%. In conclusion, visual assessment of intra ventricular flow patterns was feasible and allowed discrimination between normal and diseased ventricles.