The techniques of multiple FISH (M-FISH) or fluorescence in situ hybridization with different color assignment for all and each of the human chromosomes, and multiple BAND (M-BAND) or hybridization with different color assignment for each chromosomal band, allow the identification of some alterations that would not be possible to distinguish with classical banding techniques, like the origin of the chromosomal material that constitutes a (non identifiable) marker chromosome or confirming the constitution of the multiple and simultaneous aberrations that occur in cancer cells. We communicate five complex cytogenetic cases that benefited by the employment of this diagnostic strategy, allowing to corroborate or reformulate a previous given conclusion (Rev Méd Chile 2002; 130: 511-18)