Identification of the HLA system is important in anthropological and immunological studies. This paper proposes a simple index typing method to perform the assignment of HLA serological data. It is parsimonious and able to deal with the data of cross-reacting antigens and ill-defined sera. The method is illustrated by an example of the application of the Chinese HLA-A system in Taiwan. A general FORTRAN program for analysing the typing process is available on request from the first author.