Background: assessment of RV function is a major component of the management and prognostication of heart failure (HF) patients. Its complexity makes this task difficult and therefore not appropriately considered. Right ventricular outflow tract fraction (RVOT FS) can serve that purpose if done. The functional capacity of a HF patient must always be assessed and decision made on that basis. Aim of the study: this study aimed to investigate the applicability of RVOT FS in assessment of RV function and also its relation to functional capacity. Patients and methods: seventy-one (71) patients with heart failure with reduce ejection fraction (HFrEF) were studied prospectively and nineteen (19) control healthy individuals (normal ECG, normal left and right ventricular function and no cardiac risk factors). A 2D guided M-mode was taken in the parasternal short axis view to determine RVOT FS and a six-minute walk test (6MWT) was done to determine their functional capacity. Results: there was a reduced RVOT FS reduced in the HFrEF group (p value =0.005), 6MWT D was reduced in the HFrEF group (p value <0.001), there was a positive correlation of RVOT FS with RVFAC (r=0.839, p value<0.001) TAPSE (r=0.830, p value<0.001), S'(r=0.830, p value<0.001) 6MWT D (r=0.953, p value<0.001) and a negative correlation with RIMP(r=-0.867, p value<0.001), RV FLS(r=-0.878, p value<0.001), SPAP(r=-0.633, p value<0.001). 6MWTD with RVFAC (r=0.851, p value<0.001) TAPSE (r=0.825, p value<0.001), S' (r=0.837, p value<0.001), RVOT FS (r=0.953, p value<0.001) and a negative correlation with RIMP (r=-0.827, p value<0.001), RV FLS (r=-0.902, p value<0.001), SPAP (r=-0.621, p value<0.001). RVOT FS between HF subgroups significant (p value<0.001). Conclusion: RVOT FS is a simple and reliable parameter that can be used in assessment of RV function and has very positive correlation with functional capacity assessed by 6MWT.