<p>Background: The purpose of the study was to investigate the frequencies and types of Y chromosome microdeletions in infertile men and to analyze the relationship between the levels of reproductive hormones and Y microdeletions.<br /> Methods: A total of 1,226 infertile men were screened for Y chromosome microdeletions using multiplex PCR assay. Karyotype analysis was performed on peripheral blood lymphocytes with standard G-banding. Serum reproductive hormone levels were measured.<br /> Results: Out of 1,226 infertile patients, 134 (10.93%) had Y microdeletions. One hundred seven of 765 (13.99%) non-obstructive azoospermic patients and 27 of 133 (20.30%) severe oligozoospermic patients had Y microdeletions. Among the 134 infertile men with Y microdeletions, the most frequent microdeletions were detected in the AZFc region, followed by AZFbc, AZFb, AZFa, AZFabc(Yq), Yp(SRY)+Yq, and partial AZFc regions. Karyotype analysis was available for 130 of the 134 patients with Y microdeletions. Of them, 36 (27.69%) patients had sex chromosomal abnormalities. Levels of FSH and LH in patients with AZFc microdeletion were significantly lower, while those in patients with Yp(SRY)+Yq were significantly higher than in patients without Y microdeletions. Level of testosterone in patients with AZFabc(Yq) or Yp(SRY)+Yq was significantly lower than that in patients without Y microdeletions. However, there was no significant difference in the levels of reproductive hormones between all patients with and without Y microdeletions.<br /> Conclusion: These results highlight the need for Y chromosome microdeletion screening for correct diagnosis of male infertility. Obtaining reliable genetic information for assisted reproductive techniques can prevent unnecessary treatment and vertical transmission of genetic defects to offspring.</p>