The 70-year-old denies 11 charges relating to seven alleged victims, aged from 14 to 19, between 1966 and 1984.
Yesterday, jury selection began at Southwark Crown Court and it is expected that the prosecution case will be opened by Rosina Cottage QC today.
Outside court, Mr Clifford said the 15 months since his arrest had aged him. He said: "It has been for 15 months a very dark cloud for myself, my family and loved ones."
Eighteen potential jurors were chosen yesterday from a pool of about 60 and a final panel is due to be sworn in today.
Mr Clifford, from Hersham in Surrey, listened to proceedings through a hearing loop from the glass-walled dock.
Judge Anthony Leonard QC told the potential jurors: "The trial cannot be heard without a jury.
"It is a fundamental principle of our justice system that someone accused of a serious offence is tried by a jury selected at random."
He said sitting on a trial expected to last up to six weeks might be "a considerable burden", but that jurors might find service "an interesting and responsible" experience.
Clifford, whose clients include Simon Cowell, was arrested in December 2012 and charged last April.