Subgroups which are the union of two and three conjugacy classes were studi
ed previously in Sharyari and Shahabi (Bull. of Iranian Math. Sec. 1999, 25
(1), 55-66; J. Algebra 1998, 207 (1), 326-332). In this article we will de
termine the structure of subgroups which are the union of four conjugacy cl
asses.