Many Asian and African constitutional and statutory texts use the phrase personal laws in order to determine the rules applicable to family matters such a marriage, divorce, maintenance and in some countries inheritance. However, this term is extremely vague and often without a clear definition in the legal texts. This paper tries to show the high degree of un-determination of the statutory references to personal laws. This chaotic situation can be explained by historical and political factors. Nevertheless, the paper proposes to stipulate a conventional definition of personal laws in order to facilitate the comparison between the Asian and African countries with a plurality of personal laws. Based on common features of these legal systems knowing a plurality of personal laws, such a definition can be useful for practical as well as for theoretical purposes.