Young girls were sexually exploited by a group of men who subjected them to depravity and perversion, a court heard.
Six girls were used by men, including nine defendants from the Oxford area, the Old Bailey jurors were told.
One victim was only 12 when she was forced into prostitution. The court clerk was allowed to sit as he took half an hour to read the charges.
Noel Lucas QC, prosecuting, said: "This case involves the sexual exploitation of children - young girls - by groups of men in the Oxford area."
The men deny the 51 counts, including rape, trafficking and organising prostitution between 2004 and last year.
The accused include two sets of brothers, Akhtar Dogar, 32, and Anjum Dogar, 30, and Bassam Karrar, 32, and Mohammed Karrar, 38. The others are Kamar Jamil, 27, Zeeshan Ahmed, 27, Assad Hussain, 32, Bilal Ahmed, 26, and Mohammed Hussain, 24.
The trial is expected to last until April. The defendants are all in custody.
Mr Lucas added: "The defendants, and others not before the court, used and abused the six complainants persistently over long periods of time, sometimes in groups, for their own sexual gratification and the sexual gratification of others. The depravity of what was done to the complainants was extreme." He told the jurors that the details of the case would make them uncomfortable.
Mr Lucas said the men "actively targeted vulnerable young girls from the ages of 11 or 12". Sometimes the abusers would come across them while they were playing truant or out drinking.
He added: "There is evidence that the men deliberately targeted children who were out of control. They also targeted children who had been sent to live in care homes for precisely that reason. Some of the girls had been sexually exploited by other men, before they encountered these defendants. Some girls already being abused by the group were tasked to find other girls for the group." He said the girls were chosen because they had troubled upbringings which made it less likely that anyone would have parental control over them or be looking for them.