The royal commission into child sexual abuse has referred more than 1,500 matters to authorities, straining the resources of police forces around the country, one of its hearings has been told.

Justice Peter McClellan, who chairs the Royal Commission into Institutional Responses to Child Sexual Abuse, told a hearing in Sydney that 1,659 matters had been passed on to police to consider for further investigation.

Prosecutions have been brought against 71 people.

"Because of the volume of references, the resources of the various police forces have been placed under significant pressure," Justice McClellan said.

"I understand a great many references are awaiting investigation, or the investigations are underway but not complete."

Justice McClellan said the commission had received information about more than 4,000 institutions, but it was impossible to hold public hearings into all of them.

"We have carefully selected the institutions we have publicly investigated with a view to providing the Government, the institutions and the public with an understanding of the nature of the problems which we have identified," he said.

"The case studies have been selected to ensure an appropriate geographical spread and also an appropriate reflection of the type of institution where survivors were abused."

Commissioners have also met abuse survivors in 5,866 private sessions, with another 1,616 people yet to be seen.

The commission is today beginning a public hearing into how Catholic authorities dealt with allegations of abuse by former priest John Farrell.

It will examine the responses of the Catholic dioceses of Armidale and Parramatta, and a Sydney special issues group.

Justice McClellan said it was expected to be the royal commission's final hearing specifically relating to Catholic institutions.