The Historical Association said the exams watchdog was planning to scrap or reduce the project element, which it believes is vital in helping students gain the skills they need to become historians.
This involves pupils choosing a topic, framing a research question and investigating it, often working in specialist libraries or conducting interviews, keeping a log of their work and writing up their findings, sometimes in controlled conditions.
Sean Lang, the association's honorary secretary, said: "It is often a better measure of the student's true ability as a historian than the sometimes rather contrived or artificial exercises on exam papers."
University historians also oppose the move because the studies, often used by students for their admissions interviews, are considered an important part of their intellectual development.
Ian Archer, a history lecturer at Keble college, Oxford, said: "Losing the personal study would mean students would be less fully developed as historians when they arrive.
"It enables students to get hold of a project that they think is their own and use practical and problem-orientated skills that they might not otherwise develop."
Individual history assignments were pioneered in the 1970s by the University of Cambridge Local Examinations Syndicate and now feature as an optional part of history A-levels set by all four exam boards in England and Wales.
The Historical Association said it had learned from senior sources in the Qualifications and Curriculum Authority that assignments were being dropped as part of a review of the 16-to-19 curriculum due to be announced at the end of July. This will reduce the number of units at A-level from six to four and is expected to end coursework and internal assessment in history.
Mr Lang said the personal studies were not the same as coursework. He said that the studies helped to spark pupils' interest in history.
"It is very different to the preparation for an exam with that dull sort of rote learning," he said. "Allowing pupils to choose their own topic is a really high motivating factor and there is a clear link between motivation and results."
A QCA spokeswoman said discussions were taking place with subject experts to finalise new A-level arrangements.
She said: "One of the issues is around the personal study component of the current A-level, and recommendations on this will be published later in the year."