Verticillium wilt, caused by Verticillium dahliae, is the most serious disease in olive cultivation areas in Egypt. Thirty six (36) isolates of V. dahliae from olive (Olea europea L.) trees originating from eight regions of Egypt were taken for vegetative compatibility analysis using nitrate non-utilizing (nit) mutants. One isolate did not produce a nit mutant. Thirty five (35) isolates yielded nit mutant, they were tested for vegetative compatibility by observing heterokaryon formation among complementary nitrate-nonutilizing (nit) mutants. Among 569 chlorate-resistant sectors obtained, only 370 were Nit mutants. Three types of Nit mutants were obtained (Nit1"251", NitM"101" and Nit3"18") on the basis of the fungal phenotype. Nit1 mutants were the most frequent (67.8%), followed by NitM (27.3%) and Nit3 (4.9%).  Based on their ability to form heterokaryons, all 35 olive pathogenic isolates were grouped into a three vegetative compatibility groups. where  include VCG1 five isolates “1, 2, 6, 9, 11", VCG2  twenty one isolates" 3, 4, 5, 7, 8, 12, 19, 27, 20, 16, 10, 13, 14, 15, 17, 21, 22, 23, 25, 26, 24" and VCG3 nine isolates “18, 28, 29, 30, 31, 32, 33, 34, 36.