Preprint usage is growing rapidly in the life sciences; however, questions remain on the relative quality of preprints when compared to published articles. An objective dimension of quality that is readily measurable is completeness of reporting, as transparency can improve the reader’s ability to independently interpret data and reproduce findings. In this observational study, the authors compared random samples of articles published in bioRxiv and in PubMed-indexed journals in 2016 using a quality of reporting questionnaire. They found that peer-reviewed articles had, on average, higher quality of reporting than preprints, but the difference was small. Carneiro and colleagues also found larger differences favoring PubMed in subjective ratings of how clearly titles and abstracts presented the main findings and how easy it was to locate relevant reporting information. The authors concluded that quality of reporting in preprints in life sciences is within a similar range as that of peer-reviewed articles, albeit slightly lower on average, supporting the idea that preprints should be considered valid scientific contributions. An ongoing second phase of the project is comparing preprints to their own published versions in order to directly assess the effects of peer review.