Anshen Dyer, the London architect specialising in healthcare and research, is to be taken over by US-based Anshen & Allen, one of its two parent companies.
It is understood that Anshen & Allen bought out Dyer, the practice's other parent, after differences over business strategy.
Dyer is a general practice and Building understands that Anshen & Allen wanted to spread the joint venture's remit beyond hospital, science building and laboratory design. This could have led to Anshen Dyer to compete with Dyer.
It is also understood that a merger between Dyer and Anshen was discussed, but ruled out.
Anshen Dyer, which will be renamed Anshen & Allen, intends to promote itself as the world's largest architect devoted exclusively to healthcare, research and educational buildings.
It has an annual fee income of £12m and 125 staff. It is now starting work on large hospital projects in Ireland, Italy and Sweden.
Derek Parker, one of the founders of Anshen Dyer, will be chairman of Anshen & Allen's UK operations. Kieran Breen will replace Dale Sinclair as managing director in London.
No Anshen Dyer staff will be transferred to Dyer and no redundancies will be made.
John Cooper, healthcare director at Anshen Dyer, said: "Restructuring in this way will mean greater opportunities and flexibility in achieving goals worldwide."