New Zealand Rugby Union and Rugby New Zealand 2011 Ltd chairman Jock Hobbs has stood aside his roles because of ill-health.
Mr Hobbs, 50, was diagnosed with leukaemia last year, when it then described as chronic, rather than acute.
However, NZRU chief executive Steve Tew says Mr Hobbs's condition now requires treatment and has asked that the family be given privacy to cope with the situation.
Mr Hobbs played 21 tests for the All Blacks from 1983 to 1986 and also captained the side. He retired after a series of concussions.
The New Zealand Rugby Union board has elected Mike Eagle as acting chairman. Mr Tew says the board will meet at the end of May to assess whether Mr Hobbs is able to return to work.
Brian Roche will act as chair of Rugby New Zealand 2011 Limited, the company organising next year's Rugby World Cup.