Abstract: Knowledge about telomere length is highly relevant in cancer and age related research. Currently applied methods for determining telomere length are subject to several drawbacks preventing fast and reliable information concerning telomere length. The present invention relates to a method for determining telomere length which is fast and reliable. The method is PCR based and may advantageously be performed in a “one tube system”, whereby time consuming and inconvenient handling steps are avoided. The method comprises annealing of up- and downstream tags to telomere fragments and subsequent PCR amplification of telomere fragments using primers having a sequence complementary or identical to at least part of the up- and downstream oligonucleotide tags.