Ascochyta blight (AB) disease, caused by the fungus Ascochyta rabiei (A. rabiei), is a major yield limited factor for chickpea production in Australia and around the world. The aggressiveness of 6 A. rabiei isolates was identified using 3 chickpea (Cicer arietinum L.) varieties (Jimbour, Flipper and Yorker). These AB isolates were isolated from chickpea fields in northern NSW, one of the major chickpea production regions in Australia. Each of the six isolates produced a different aggressiveness pattern and isolate 4859 was found to be the most aggressive. The AB resistance in 16 international and Australian chickpea varieties was then investigated by inoculating the plants with the most aggressive isolate and a mixture of the other 5 isolates. Resistance to both the most aggressive isolate and the mixed isolate has been identified in 8 lines (ICCV 98813, Flipper, ICCV 05111, ICCV 98801, Howzat, Jimbour ＃1, ICCV 06108 and ICCV 98818) while 7 entries (Jimbour, ICCV 96852, ICCV 06107, ICCV 98816, Yorker, FLIP97-114C, ICCV 96853) were moderately resistant. Only one genotype (Bumper) appeared to be susceptible to both inoculums. There was large variation observed in the pathogenicity of the isolates suggesting that the 6 AB isolates represent several different pathogen strains. Significant differences in leaf infection rate, plant infection rate, plant death rate and disease development were identified among the chickpea genotypes tested. These findings suggest that the chickpea genotypes tested carry different resistant genes, which can be exploited in breeding programmes to develop high levels of disease resistance.