Objective: Male infertility is believed to be associated with deletions on the Y chromosome as firstly has been reported by Tiepolo and Zuffardi. The microdeletions are commonly occurring in the specific region in the chromosome Y has been called as AZF, a region that thought to contain some genes are involving in spermatogenesis (Dada et al., 2003). The AZF region is subdivided into three non-overlapping sub-regions called AZFa in the proximal portion (interval D3-D6), AZFb in the intermediate region (D13-D16) and AZFc in the distal region (D20-D22) (Foresta et al., 2001). They are strongly associated with spermatogenic defects, such as azoospermia and oligozoospermia (Ferrás et al., 2004a; Foresta et al., 2005). Microdeletions in the AZF region are frequently found in patients with azoospermia. The incidence of these microdeletions has been found to vary from 3 to 55% in Yq of patients are diagnosed with infertility (Foresta et al., 1998; Vogt, 2004). Although a high percentage of infertile men with microdeletions in the Y chromosome are not able to produce children by natural mechanisms of reproduction, there can be transmission of the father’s infertility problems to his sons, when they are produced by assisted reproduction. This predisposition for infertility can include gradual alterations in spermatozoid production, so that a young man with oligozoospermia later becomes azoospermic (Kihaile et al., 2005). Materials and Methods: We examined microdeletions in the Y chromosomes of men with azoospermia and severe oligozoospermia in Khuzestan province. Thirty-one patients with azoospermia and 47 with severe oligozoospermia were analyzed by PCR. The patients were classified according to alterations detected in three consecutive spermograms, based on the WHO technique (1999), into groups with non-obstructive azoospermia and those with severe oligozoospermia (≤5 x 106 sperm/mL) and patients’ blood were collected. Genomic DNA was extracted from peripheral blood lymphocytes and microdeletion analysis was made of the regions AZFb and AZFc sequence-tagged sites. The PCR product was run by electrophoresis on a 1.5% agarose gel impregnated with ethidium bromide at 5µg/mL and visualized under UV light. Results: Among the 78 patients with azoospermia or severe oligozoospermia, 11 patients that have been diagnosed with severe oligozoospermia were positive for microdeletions, from them nine patients (21.2%) showed deletions in the AZFb region and two patients (4.2%) in the AZFc region.The ages of the azoospermic patients varied from 23 to 47 years, with a mean of 31 years. Patients with severe oligozoospermia ranged from 22 to 38 years, with a mean of 32 years. Conclusion: We conclude that microdeletions in Yq could be one of the important causes of idiopathic male infertility and our findings support previous studies.