Sexual function is how the body reacts in different stages of the sexual response cycle, or as a result of sexual dysfunction. Relevant aspects of sexual function are defined on the basis of a modified version of Masters and Johnson's work. The aspects of sexual function defined as being relevant to the assessment include sexual desire, erection, orgasm and ejaculation. Guidelines for assessing sexual function are suggested and divided into four stages:
Stage 1 deals with the documentation of the defined aspects of sexual function. The main questions are:

1. Is the function intact? For example: Have there been any occurrences of erections or orgasms during a given period of time?
2. If the function is intact, what is the frequency and/or intensity of the function? For example: How often has the person had an orgasm or erections during the given period of time and how intense is the orgasmic pleasure and erection stiffness compared to youth or the best period in life. The suggested explanations for the absence or waning of functions at this stage are physiological and psychological.