為了幫助人們解決性功能障礙，性治療師需要確切知道障礙是什麼。簡單地詢問病人或客戶姓名或他們的症狀，儘管始終是必要的，卻是不夠的。許多男女不明白他們自身的生理機能，會誤解或曲解自己的症狀或有不切實際的期望。所以：除非通過提供知識或提供一些簡單的建議就能夠容易解決所面臨的問題，尚需要詳細的診斷。
診斷通常經過兩個步驟：

1. 身體檢查
2. 詳細問診(“採集既往性生活史”)

In order to help people with their sexual problems, therapists need to know what exactly these problems are. Simply asking the patients or clients to name or define their problems - while always necessary - is usually not sufficient. Many women and men do not understand the functioning of their own bodies, misunderstand or misconstrue their symptoms or have unrealistic expectations. Therefore: Unless the problem can easily be solved by giving information or making some simple suggestions, a detailed diagnosis is necessary.
The diagnosis usually proceeds in two steps:

1. A physical examination
2. A detailed interview ("taking a sex history")