Amersham, the medical research firm, has agreed to be taken over by US giant General Electric (GE).
The deal values Amersham at £5.7bn ($9.12bn), the company said.
Chief executive Sir William Castell said: "The £8-a-share offer we received represents excellent value for our shareholders."
He added the deal would also offer "good opportunities for our employees to continue their drive for innovation".
The new combined company will be known as GE Healthcare Technologies and will be led by Sir William.
Amersham is one of the world's leading firms in pioneering research and new technologies to fight diseases.
The £8-a-share offer represents a premium of more than 45% on Amersham's share price prior to bid speculation earlier this week.
GE said Amersham would add new technology platforms to build on work by its own GE Medical business in diagnostic imaging and healthcare services.
FTSE 100 firm
Sales of £1.6bn in 2002
Formed in 1997 by three-way merger with UK, Norway and Swedish firms
Offices in 50+ countries
GE chief executive Jeffrey Immelt said: "GE and Amersham will be an exciting combination of talents, businesses and technologies."
The US firm added it had absolutely no plans to spin off any of Amersham's businesses following the deal, a claim backed by Amersham's boss.
GE also said no job cuts were planned for Amersham's research and development or sales areas, adding any losses would be focused on back office overlaps.
The UK company was the first big privatisation under the Conservative Government - back in February 1982, when it was valued at £70m.
The group, which employs 10,000 people across the globe, is seen as a world leader in medical diagnostic equipment and biotechnology.
It already has close ties with the medical systems business of General Electric - one of the biggest companies in the world.
The deal is subject to approval by shareholders and competition authorities in Europe and the US.
The takeover could spark concerns that a UK firm with a strong research and development record is set to move into American ownership.
However, General Electric is set to move the headquarters of its medical division to the UK in a bid to combat any worries.
Sir William said: "The thing that we've found with GE is that they have a shared vision and their skills are complementary to what we need.
"That to me is more important than retaining the British identity.
"Our corporate headquarters will be based here, and we'll be operating a global company from here - just as we have for the last 14 years."
The Amersham takeover is the latest in a string of deals made by GE.
Earlier this week, the US group finalised a deal to merge its US broadcasting arm NBC with US
entertainment assets of Vivendi Universal into a new US media giant called NBC Universal.