Richard Brewster, chief executive of cerebral palsy charity Scope, has resigned after leading the organisation for the past seven years.
Brewster will have worked for the charity for 14 years when he departs in February 2003.
He is leaving the charity to move to the US, where his wife is establishing the US arm of a management consultancy firm.
The charity will begin actively seeking a replacement in the autumn.
Brewster is now looking for a role in the US not-for-profit sector.
He joined Scope in 1989 as director of marketing and led the renaming of the charity from The Spastics Society to Scope. Brewster began his voluntary-sector career with Oxfam after working for ICI.