Abstract Introduction An important mechanism of ED is vascular endothelial function injury or disorder and low-intensity extracorporeal shock wave therapy (LI-ESWT) can stimulate and promote vascular regeneration, especially in failed PDE5i. The present selection criteria used for EDSWT are subjective in the form of IIEF, EHS or SEP with no objective definition of the extent of vascular involvement. There is a need to comprehensively evaluate ED including the extent of local and systemic involvement. Objective To develop objective parameters of validated assessment of endothelium in men with organic erectile dysfunction and to evaluate if they could be used to plan accurate PDE5i, non-invasive modalities of treatment. Methods In a prospective study, patients who were earlier evaluated and had vasculogenic ED and failed PDE5i treatment were clinically re-evaluated with questionnaires and CDDU. Additionally endothelial function and large arterial stiffness was assessed with the Vendys (reactive hyperaemia) & Sphygmocor (central arterial pressure waveform analysis). Categories identified were, endothelial dysfunction by Vendys, Aortic augmentation index abnormality by Sphygmocor (age corrected), combined abnormality with poor scores with or without metabolic comorbidity. All three groups underwent LI-ESWT with low dose PDE5 inhibitors with a revised protocol. Results Validation of diagnostic tools was done in thirty five patients aged 48.24 ± 4.6 years (mean ± SD) with a mean IIEF score of 8.4 were evaluated by the three techniques. Positive predictive value (PPV) of the three techniques was similar, in the range 89-91% and a negative predictive value (NPV) around 41-45%. CDDU had highest sensitivity at 85%, but low specificity of 55%, followed by Sphygmocor® at 77% and Vendys at 75% and the latter techniques had better specificity of 70%. Parameter Penile Doppler SphygmoCor® Vendys® Value 95% CI Value 95% CI Value 95% CI Sensitivity 85 % 70.1-94.3 77.5 % 61.5-89.1 75 % 58.8-87.3 Specificity 55.6 % 21.2-86.3 70.0 % 34.7-93.3 70 % 34.7-93.3 Positive likelihood Ratio 1.91 0.91-4.02 2.58 0.99-6.76 2.50 0.95-6.55 Negative likelihood Ratio 0.27 0.11-0.69 0.32 0.16-0.65 0.36 0.18-0.70 PSV (N) IIEF Class (N) % < 25 (22) Severe (18) 81.82 44.00 Mod (3) 13.64 Mild (1) 4.55 25-30 (17) Severe (0) 0.00 34.00 Mod (14) 82.35 Mild (3) 17.65 CDDU Vs IIEF score The patients were grouped into three arms Vendys abnormality, Sphygmocor and combined; for Li-ESWT treatment (15 each). Pre and Post questionnaire based assessment was done and maximum improvement of IIEF was in the Alx abnormality arm with poor results in combined abnormality. Conclusions The aortic strain index and distensibility index were impaired in patients with ED. Vendys® SphygmoCor® are new tools in diagnosis of ED and superior to penile Doppler or questionnaire assessment. Li-ESWT is most beneficial in patients with Aortic elastic abnormality probably due shock wave effect on sheer stress of vessels by altering vessel wall pulsatality and resistivity index. Disclosure No