The use of fluorescence in-situ hybridization (FISH) in decondensed spermatozoa from carriers of structural chromosomal abnormalities provides a way to estimate the amount of unbalanced products. This methodology has become a tool of special interest for a better approximation of the reproductive competence of the carriers. Although there is no discussion regarding the cytogenetic value of the information obtained, the usefulness of performing individual sperm FISH studies must be weighed depending on the object of the study. In this paper, we introduce some considerations concerning the convenience of a routine application of sperm FISH analysis in the major populations of structural reorganization carriers. For each group, the significance of the information that can be obtained and its relevance for genetic reproductive advice are discussed.