The 13-18% of the couples in reproductive age gets to present some kind of fertility problem, the male factor participates in near 50% of the cases. The microdeletions in the Yq chromosome occupy single the 7,6%; severe oligozoospermia and azoospermia are related with these alterations. The structure of region AZF of Yq is divided in AZFa, AZFb, AZFc and AZFd. The microdeletions can be simple or combined, the microdeletion AZFc (59-65%) is the commonest. In cases with severe oligozoospermia (or azoospermia), study of microdeletions in Y chromosome is suggested. ICSI with selection of sex, would be the treatment adapted in these cases, is in phase of study.