Quantitative fluorescence in situ hybridization (Q-FISH) is a complex technique for the quantitative evaluation of telomere length on cell preparations or on human tissues. The samples are stained with a fluorescent peptide nucleic acid (PNA) probe against the telomere oligonucleotides (sequence 5'-TTAGGG-3'). The measure of the telomere length is carried out using a fluorescence microscope equipped with a sensitive CCD camera and analyzing the pictures with a computer software that can perform fluorescence intensity measurements. Here, we describe the most used protocols to stain, acquire, and analyze fixed human cells in order to evaluate their telomere length
