I've had the "why doesn't RefWorks include URLs in my APA bibliography" question a few times now. I've included my answer to a student, below, in case you've also been asked the same. I think this is why it's happening, but if anyone has any other ideas let us all know.
I believe that what is happening is not a problem with RefWorks, per se. The RefWorks filter does use the proper APA 5 format, and if you read the style guide closely, you'll notice that it makes a distinction between "internet articles based on print sources" and "articles in internet-only journals" (from http://www.apastyle.org/elecsource.html):
71. Internet articles based on a print source
"At present, the majority of the articles retrieved from online publications in psychology and the behavioral sciences are exact duplicates of those in their print versions and are unlikely to have additional analyses and data attached. This is likely to change in the future. In the meantime, the same basic primary journal reference (see Examples 15) can be used, but if you have viewed the article only in its electronic form, you should add in brackets after the article title "Electronic version" as in the following fictitious example:VandenBos, G., Knapp, S., & Doe, J. (2001). Role of reference elements in the selection of resources by psychology undergraduates [Electronic version]. Journal of Bibliographic Research, 5, 117-123.
If you are referencing an online article that you have reason to believe has been changed (e.g., the format differs from the print version or page numbers are not indicated) or that includes additional data or commentaries, you will need to add the date you retrieved the document and the URL.VandenBos, G., Knapp, S., & Doe, J. (2001). Role of reference elements in the selection of resources by psychology undergraduates. Journal of Bibliographic Research, 5, 117-123. Retrieved October 13, 2001, from http://jbr.org/articles.html"
In a nutshell, this is a bit of a gray area, and I'm supposing that RefWorks is not able to make the kind of judgement call required by APA in citing URLs. Some instructors may ask that you always include the URL in your bibliography, and In this case, you would simply have to add that information to your bibliography manually in your word processor after it has been created by RefWorks.Posted by Sherri at December 14, 2006 12:32 PM