What is likely to be Germany's last big Nazi-era trial is getting under way in the city of Munich.
The defendant is John Demjanjuk, a Ukrainian-American accused of helping to murder almost 30,000 people at the Sobibor death camp in occupied Poland during the Second World War.
The BBC reports it is probably the last time a Nazi war crime is tried with a living defendant.
The trial is expected to last until May and, if found guilty, Mr Demjanjuk could be sentenced to 15 years in jail.
A retired US car worker, he is formally charged with 27,900 counts of accessory to murder.
Prosecutors say that as a camp guard at Sobibor, he pushed thousands of Jewish men, women and children to their death in the gas chambers.
Mr Demjanjuk was born in Ukraine and captured by the Nazis while fighting in the Soviet army. He denies even being at Sobibor.
The trial's first session was delayed, AFP news agency said, as large numbers of people tried to gain access.