Background: Cochrane reviews are regarded as being scientifically rigorous. However, the proportion of Cochrane protocols that are published as Cochrane reviews and the average time to their publication remains unclear. This information is important because consumers, clinicians, and policy-makers increasingly use Cochrane reviews as part of their decision-making process. If the time to publication of Cochrane reviews is affected by factors such as statistically significant results, this may lead to inaccurate decisions. Objectives: To identify the frequency of published and unpublished Cochrane reviews, determine their time to publication, and examine which factors are associated with time to their publication. Methods: A cohort of new Cochrane protocols published in Issue 2, 2000 was assembled. The publication status of these reviews was tracked up to Issue 1, 2008 in The Cochrane Library. A 45-item data abstraction form was developed and pilot-tested by two people, independently, on a random 5% sample. The data were subsequently abstracted by one person. Data included type of result, type of conclusion (e.g., positive), and funding status. Data were analyzed descriptively and via multivariate analyses. Results: There were 130 new Cochrane protocols published in Issue 2, 2000. After excluding 12, 25/118 (21.2%) were unpublished and 93/118 (78.8%) were published as Cochrane reviews. Thirty-seven reviews (39.8%) were updates. The median time to publication was 1.6 years (range: 0.1 to 7.3 years). Factors associated with longer time to publication included an author change between the protocol and final review (p = 0.003) and the review having two protocols (p = 0.026). An updated review was associated with a shorter time to publication (p = 0.006). Conclusions: Although statistically significant results and positive conclusions were not associated with time to publication, only 80% of Cochrane protocols were published as final Cochrane reviews. The median time to publication was 19 months, yet some reviews took much longer. Strategies to decrease time to publication, such as providing support to reviewers when a change in authorship occurs, should be considered. Future research should examine the factors that predict unpublished Cochrane reviews.