Introduction: It was reported that a more generalized peripheral atherosclerotic process is associated with a severer penile arterial insufficiency(PAI), and this in turn was correlated well with decreased blood supply in more important arteries like the coronary and carotid arteries. Aim We investigated the risk factors for penile arterial insufficiency(PAI), which is a known cause of erectile dysfunction (ED). Methods: Patients who attended our urology clinic complaining of ED for more than 6 months, were prospectively enrolled in this study in one year period. Patient consent was taken and ethical committee approval. Complete medical history and thorough general and local examination including body mass index (BMI), Peyronie’s disease (PD)and penile size measurements (length and girth) were done for all of them. Laboratory tests included testosterone, lipid profile, and glycated haemoglobin (HbA1c). Penile duplex ultrasound study (PDU) was done for all patients after intra-cavernosal injection (ICI) with Alprostadil. peak systolic velocity (PSV)and end diastolic velocity (EDV) were measured after 15 minutes. Statistical analysis was done using SPSS. Results: A total of 440 patients were enrolled in this analysis. The mean age was 48(23-81), and the mean BMI was 30(18-51). Older patients had lower PSV (r=-0.361, P=0.000) and higher EDV (r=0.174, P=0.001) and both correlations were highly statistically significant. Diabetics had lower PSV (r=-0.318, P=0.000) and higher EDV (r=0.139, P=0.008) which were also highly statistically significant. Smokers had lower PSV (r=-0.140, P=0.008) and higher EDV (r=0.178, P=0.001) which were highly statistically significant. Men with longer penises measured skin to tip, had lower EDV (r=-0.119, P=0.024) which was also significant. Interestingly there was neither significant correlation between BMI and PSV (0.16, p=0.745) nor significant correlation between testosterone and PSV (0.029, p=0.552). Also, there was no correlation between PSV and either dyslipidaemia or Peyronie’s disease. Conclusions: Our study highlights key risk factors - Increased age, tobacco consumption, DM and hypertension - are factors that have a statistically significant negative impact on penile haemodynamics. Of these, tobacco consumption, good diabetic control and hypertension are potentially modifiable and should form part of any treatment plan for erectile dysfunction. Other risk factors – increased BMI, low testosterone, PD and penile size – had no statistically significant impact on penile hemodynamics. This allows for targeted advice that can be given to patients who present with this very common problem. Ultimately, good vascular health goes hand in hand with good erectile function. SOURCE OF Funding: none