The search for neutrinoless double beta decay might be the only window to observe lepton number violation.

Its observation would favour the leptogenesis mechanism for the explanation of the baryon asymmetry of the universe  and  is therefore considered to be of highest relevance.

The isotope 76Ge has historically been most important for this search and the ongoing experiment GERDA has demonstrated the lowest background.

The talk reviews the motivation, the current status of experiments and future programs.