Premature ejaculation is the lack of ability to control ejaculation during sexual intercourse in men, who ejaculate before or just after penile penetration into the vagina or shortly after penetration, resulting in dissatisfaction and distress. Since Masters and Johnson defined premature ejaculation in 1970, there have been many different versions of the definition of premature ejaculation internationally, which just shows that the medical understanding of premature ejaculation has been under constant improvement. Currently, most international scholars use intravaginal ejaculatory latency (IVELT) as an important objective indicator for the diagnosis and efficacy of premature ejaculation. Intravaginal ejaculation latency is the length of time from penile insertion into the vagina to the time of ejaculation during sexual intercourse. Generally, the intravaginal ejaculation latency of a certain number of intercourse over a period of time better reflects the patient’s condition, i.e., it is difficult to reflect the total condition of the patient by one or two intercourse. Therefore, if a patient with premature ejaculation can record the duration of sexual intercourse (i.e. intravaginal ejaculation latency, generally accurate to the second) several times (generally 5 to 10 times) before the consultation and give it to the doctor during the consultation, it is certainly very meaningful for the doctor to accurately determine the condition. I recommend that premature ejaculation patients do this homework before coming to my clinic. The patient should prepare a stopwatch (a stopwatch used in sports, many electronic watches have this function, and many cell phones can also call up the stopwatch function), a blank piece of paper, and a pen. Before intercourse, zero the stopwatch, press the stopwatch when the penis is inserted into the vagina to start timing, and then press the stopwatch again when ejaculation is imminent to stop timing. When intercourse is over, record the length of time shown on the stopwatch on the paper. During intercourse, the man can hold the stopwatch in his hand, or the woman can hold the stopwatch and the man can signal the woman when the penis is inserted into the vagina and when he is about to ejaculate, and the woman can assist in timing. Time the latency of intravaginal ejaculation with a stopwatch for all intercourse (or 5 to 10 times) over a period of time (for example, two weeks or a month) and record it on a piece of paper that you remember to bring with you when you come to my clinic. Patients may say, “Doesn’t the fact that I feel that I have short intercourse time indicate my premature ejaculation condition? Why do I have to measure it? Actually, human sensation is not very accurate. Very often, what a husband says about the duration of intercourse differs greatly from what his wife says. A man’s sense of time during intercourse is often distorted. Thus, accurate recording of the time of intercourse (intravaginal ejaculation latency) better reflects the patient’s true condition. It helps the doctor to determine the condition. More importantly, after the visit, the patient should still record the time of each sexual intercourse (intravaginal ejaculation latency, to the second) in a small medical record book and give it to the doctor at the next follow-up visit. Based on the patient’s record, the doctor understands the effectiveness of treatment, identifies problems in a timely manner, and decides whether to adjust the program. It can be seen that the patient’s careful recording of the duration of intercourse (intravaginal ejaculatory latency) before and after the visit plays an important role in the diagnosis and treatment of premature ejaculation patients. In practice, to my surprise, I found that any patient who did a poor job of recording tended to have a poor treatment outcome as well. I hope every patient who comes to see me for premature ejaculation will do this homework seriously.