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The Introduction is the section of a research paper that establishes why the study was done: it states the problem, situates it against existing literature, and ends by telling the reader exactly what question the paper answers. It is the first section a reviewer reads in full, and a common reason papers draw an early “not convinced this is novel or necessary” reaction is an Introduction that never actually narrows down to a specific, answerable question.
This guide covers what the Introduction is for, the funnel structure most journals expect, and the pitfalls that most often draw reviewer criticism. For the section-by-section logic of the whole paper, see CASRAI’s IMRaD Structure entry; for the section that follows it, see Writing the Methods Section So It Can Be Reproduced.
Last verified 25 August 2026 against ICMJE’s Recommendations for manuscript preparation and standard editorial guidance from major biomedical and scientific journals.
What the Introduction Section Is For
The Introduction’s job is to move the reader from a broad topic down to one specific, unanswered question — and to justify, with evidence, that the question is both real and still open. Unlike the Discussion, which interprets what was found, the Introduction argues for why the study needed to happen at all. A reader who finishes the Introduction should be able to state, in one sentence, exactly what the paper is going to test or investigate, and why that hadn’t already been settled by prior work.
ICMJE’s manuscript-preparation recommendations describe this section’s purpose directly: it should “provide a context or background for the study (i.e., the nature of the problem and its significance)” and “state the specific purpose or research objective of, or hypothesis tested by, the study.” Everything in a well-built Introduction serves one of those two jobs — establishing context, or narrowing to the objective — and content that does neither (a full literature review, a preview of the results, a restatement of the Discussion’s implications) belongs somewhere else in the paper.
The Funnel Structure
Most empirical Introductions follow a recognizable funnel, moving from wide to narrow across three to five paragraphs:
1. Establish the Broad Context
Open with the general problem area and why it matters — the burden of a disease, the scale of a phenomenon, the practical or theoretical stakes. This section should be brief; its only job is to orient a reader who is not already a specialist in the exact sub-topic.
2. Narrow to What’s Already Known
Summarize the relevant prior work, cited specifically rather than vaguely gestured at (“prior work has examined X, Y, and Z” is weaker than naming the actual studies and what each established). This is not a full literature review — it is the minimum background a reader needs to understand what the field currently believes.
3. Identify the Gap
State explicitly what is not yet known, not yet resolved, or not yet tested — the gap this study fills. This is the pivot point of the whole section: everything before it describes what’s known, everything after it describes what this paper will do about what isn’t.
4. State the Objective, Question, or Hypothesis
End with a precise, falsifiable statement of what the study set out to do. Journals vary in whether they want this as an explicit hypothesis, a research question, or a stated objective/aim, but the paragraph should not end vaguely — a reader should be able to underline one sentence and know exactly what the Results section will report on.
5. Optional: a Brief Approach Preview
Some journals and disciplines expect a short final sentence previewing the general approach (“we tested this using a randomized, double-blind design”), though the Methods section is where that approach is actually detailed. Where a journal doesn’t expect this, it’s safe to omit.
Common Pitfalls
- Starting too broad and staying there. An Introduction that spends three paragraphs on the general importance of the field without ever narrowing to a specific gap reads as padding, and reviewers notice.
- Burying or omitting the gap. If a reader can’t point to the sentence that says “this specific thing is not yet known,” the justification for the study is missing, not implied.
- Writing a mini literature review instead of a background section. The Introduction cites what’s necessary to establish the gap; it is not the place for exhaustive coverage of every related study.
- Vague objectives. “This study explores issues related to X” is not a testable objective. “This study tested whether X predicts Y in a cohort of Z” is.
- Overclaiming novelty. Asserting a study is the first to examine something is a specific, checkable claim — it should only appear if the literature search actually supports it, since an overclaim here is one of the fastest ways to draw a skeptical reviewer.
How Long Should It Be?
There is no universal word count, and requirements vary by journal and article type — a clinical case report’s Introduction may run a single paragraph, while a basic-science paper’s may run several. As a general orientation, most journals expect an Introduction that a reader can get through in a few minutes and that ends with an unambiguous statement of the study’s objective; length that goes well beyond what’s needed to establish the gap and state the objective is usually a sign the section needs tightening rather than that the topic requires more space.
References
- International Committee of Medical Journal Editors, “Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals” — Section IV.A.3.d, “The Introduction,” icmje.org
