Erectile dysfunction (ED) is the inability to get and keep an erection firm enough for sex.1 Completely hard and fully rigid erections (GRADE 4) should be recognized as the optimal goal of ED therapy.2

1. NHS choice: Erectile Dysfunction. (2017). Available at: https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/2017 (Accessed: 20 March 2020). 2. Mulhall JP, et al. Erection Hardness: A unifying factor for defining response in the treatment of erectile dysfunction. J Urology 2006;68:17-25