Nature Cell Biology is pleased to introduce a new system by which papers are published online before they appear in print: advance online publication (AOP). We have first applied this system to publish online the original research papers that can be found in this issue, which went live as early as 19 November 2001.

Why publish papers online before they appear in print in the first place? Accepted manuscripts that have been edited and laid out by our production team are often ready for publication weeks before the print issue is available, and there is no reason at this point to delay the dissemination of the information contained in them. We feel that it is vital to provide this service, as we are aware that our authors work in competitive areas of research and that the web is increasingly used as the primary source of information for our readers.

Faster PubMed citation

In the new AOP system full text versions are provided in addition to PDFs, allowing, for example, the cross-linking of references. Significantly, as an additional service to our authors and readers, this will permit us to have original research papers listed on PubMed just a few days after they are published online. Furthermore, publishing papers without their final pagination means that we no longer have to publish them in the same order in which they appear in print, allowing us for example to publish Brief Communications before the pagination for all Articles is available.

How exactly does AOP work? Once papers are ready for publication, they receive a digital object identifier (DOI), a unique and persistent identifier. DOIs are used by more and more publishers of scientific literature, and with the increasing shift of emphasis from print to online publication, this system looks set to become a universal practice for publishing and identifying research papers. How can papers with a DOI that do not have final page numbers and an issue assigned to them be cited? After the reference citation, simply add Nature Cell Biology < publication date and paper's DOI >. Importantly, the DOI will be included in the print version and will remain associated with a manuscript, and papers can always be traced by using their DOI. In fact, papers can be accessed directly over the web by using the URL http://dx.doi.org/< Paper's DOI >.

Readers may have noted that all of the papers in this first print issue of 2002 were published online in 2001. Although there is probably no doubt that online publication dates should be considered as the dates of distribution into the public domain, at present most abstracting and indexing services (including MEDLINE and the Institute for Scientific Information) cite the print date as the publication date. Cases such as these, when online and print publication fall into different years, could particularly suffer from the ambiguity about when they were published. However, as online publishing practices evolve rapidly, such issues will undoubtedly advance accordingly and should be resolved in the near future.

In summary, we hope that our authors and readers will find the new AOP system an improved service. More information about DOIs and our new AOP system can be found on our web site at http://www.nature.com/ncb/aop/. As always, we welcome feedback and suggestions sent to cellbio@nature.com.