In one sense, there is no difference at all. Workflow is the basis of business process management (BPM) as well as business re-engineering. From that perspective, BPM is simply workflow with a lot of bells and whistles.

From another perspective, those bells and whistles are important enough to make a major difference for someone trying to make a business run more efficiently. A typical business process management application has an elaborate set of modeling tools, analytical functions and other features to handle complex projects that reach across an entire corporation.

But not always. Plexus, for example, calls itself a workflow product and it includes a fairly complete set of additional features for large projects. Workflow trade groups, such as the Workflow Management Coalition, are deeply involved in developing tools for large projects, such as an XML-based process definition language (PDF). And some BPM software offers only basic tools.

Functionally, the difference between the two terms is that companies that advertise themselves as being in the BPM business are usually aiming at big, complex projects in large corporations. Those that call their products "workflow" are aiming at more limited projects.

But not always. Perhaps the best way to look at it is that the terms overlap so much that it's virtually impossible to draw any kind of a hard line between them—not that the various vendors don't try strenuously. In fact, there's so much overlap that the terms are almost, but not quite, synonymous.