Telomeres are the structures at the ends of chromosomes, composed of repetitive sequences and associated proteins, which cap chromosome ends to maintain genomic stability. These structures are maintained by the enzyme complex telomerase in germ cells and some stem cells, but are absent in the majority of somatic cells. The consequence of this lack of telomerase in normal somatic cells is the shortening of the telomeric repeat, which results in a limited replicative life span. However, in cancer cells, which grow indefinitely, telomerase activity has been detected in a large number of different cancer cell types. This has lead to a great deal of interest in establishing techniques to measure telomerase activity, telomere length, and telomere function in both normal and cancer cells/tissue. Here we describe the TRAP (telomeric repeat amplification protocol) assay, a technique to measure telomerase activity in cells, TRF (terminal restriction fragment length) analysis to estimate telomere length, and both the anaphase bridge index and the frequency of dicentric chromosomes as indicators of telomere dysfunction.