The purpose of the present research is to study “Kamesumicchacara and ethical problems in present society”. It is the study and research of ethical problems in society which have their causes from the transgression of the third precept in the Buddhist philosophy, that is sexual misconduct or Kamesumicchacara. This research is divided into 6 chapters as follows ; Chapter 1 : Introduction Chapter 2 : Meaning, factors and causes of Kamesumicchacara Chapter 3 : Behaviors on sexual misconduct Chapter 4 : Problems and effect of the transgression of sexual misconduct Chapter 5 : Buddhist way of solution of ethical problems of sexual misconduct Chapter 6 : Conclusion and Suggestion From this research, it is found that sexual behavior of an individual in the present society trespasses the third Buddhist precept in many aspects. And several other behaviors are included in this offence. Many ethical problems and crimes are also found having their causes from this unlawful sexual intercourse. The result of the research can be summarized as follow ;- 1. The meaning of the term “Kamesumicchacara has been found in many places :- A. In commentary called Manglattha dipani, the term “Kamesu” means bad behavior of the couple, “Micchacara” means bad behavior condemned by the wise. It occurs from the volition to transgress the physical factor with the purpose to make unlawful sexual intercourse called “Kamesumicchacara”. B. In Thai dictionary of the Rajpandityasathan, it means sexual misconduct. C. In the Tipitaka, the term “Kamesu” means internal desire and external objects, “Micchacara” means immoral conduct blamed by the wise. There is also the mention of its offence that it has minor offence if it is done towards the less virtuous person, and it has major offence if done towards the higher virtuous person. 2. According to Buddhist philosophy relating to the precept of unlawful sexual intercourse, there are four factors for judgement of sexual misconduct, namely ; 1) the prohibited person for sexual intercourse, 2) the intention to do sexual intercourse with that prohibited person, 3) an attempt to do sexual intercourse with that prohibited person, 4) doing sexual intercourse with that person If anyone has completed these four factors of unlawful sexual intercourse, he is said to have committed Kamesumicchacara or adultery according to Buddhist philosophy. On the contrary, if any sexual intercourse, excluding these above mentioned factors, especially the first factor is regarded as common and natural conduct of all common people. Of these four factors of unlawful sexual conduct, the first factor is divided into two categories, one for male and another for female. There are three kinds of prohibited female for male in doing sexual intercourse : all together there are twenty kinds of females : 1. Ten kinds of the married women 2. Two kinds of included married women 3. Eight kinds of protected women There are only two kinds of prohibited male for female in doing unlawful sexual intercourse : 1. The married man 2. The recluse 3.There are two root-causes of the transgression of the precept of sexual misconduct : 1. The internal cause is inner sexual desire 2. The external cause is external objects such as human beings, attractive environment, social value etc. 4. There are many causes of sexual intercourse which transgresses the third precept of Buddhist philosophy in the present society. Some cases are transgressed by only one side. Some cases are committed by bot