Background. The Y chromosome microdeletions belong to the frequent genetical causes of male infertility. The aim of our studywas to introduce reliablemolecular genetic diagnosis of Ychromosomal microdeletions and to determine the prevalence of Y chromosomal microdeletions in Czech males with serious reproductive disorders. Methods and Results. The Ychromosomemicrodeletions were screened in 198Czech menwith serious reproductive disorders with decreased sperm count. The Y chromosome microdeletions were disclosed in 8/198 (4.0 %) examined males. The AZFc deletion type was revealed in 62,5 % (5/8) and the combined AZFc+b microdeletion in 37,5 % (3/8) of cases. Neither isolated AZFb nor AZFa microdeletion were found in any subject of the investigated group. Conclusions. Incidence of individual types of Y chromosomal microdeletions in Czech males with serious reproductive disorders was assessed. The standardisedmolecular genetic diagnosis ofYchromosomalmicrodeletions was introduced into the practice.

        Key words: male infertility, Y chromosome microdeletions, AZF region, azoospermia, oligozoospermia.