Definitions of what is primary or secondary differ across the disciplines. For the sciences, a primary source
- documents the results of original research
- is written by those who have conducted the research
- includes firsthand information about their methodologies, data, results, or conclusions.

Primary sources in the sciences:
- report original research, ideas, or scientific discoveries for the first time
- report results/findings/data from experiments or research studies
- may also be referred to as primary research, primary articles, or research studies
- are NOT meta-analyses, systematic reviews, or literature reviews - these are secondary sources
- are frequently found in peer-reviewed or scholarly journals
- should explain the research methodology used (randomized controlled trial, etc)
- frequently include methods, results, and discussion sections
- are factual, not interpretive
Examples of Primary and Secondary Sources
Primary Sources
- Research articles presenting original research (studies) published in scholarly, peer-reviewed journals
- Clinical trials
- Interviews
- Correspondence
- Patents
- Lab notebooks
- Data sets
- Theses and dissertation
- Technical reports
Secondary sources
- Summaries, critiques, or interpretations of primary literature
- Literature reviews
- Reports from prior studies
- Health information systems maintained by government health departments (These track information related to disease surveillance data, immunization coverage, and other data that provides information from monitoring of population health indicators).
- Meta-analyses
- Systematic reviews