There is increasing awareness that most work is changing, and the predominant trend is toward greater complexity, becoming known as knowledge work. Two fundamental questions remain essentially unresolved about knowledge work, which have importance to the human resource development field. First, what are the characteristics of knowledge work that make it unique from other work behaviors? Second, how should organizations develop employees to perform knowledge work? To address these questions, this article has the following goals. First, the article reviews the definitions of knowledge work and discusses four key points that provide a better understanding of the topic. Second, the article proposes a definition of knowledge work using the term knowledge-based tasks to describe instances of knowledge work. Third, the article presents an employee development system that helps individuals learn to perform knowledge-based tasks. The article concludes with a brief discussion about knowledge work and the challenges and opportunities it presents to the human resource development field. Keywords knowledge work, human resource development theory, work analysis, changes in jobs This article focuses on knowledge work and its relevance to human resource development (HRD). With few exceptions, there has been limited discussion about the relationship between these two topics (e.g., Elkjaer, 2000). Nevertheless, there is increasing awareness that most work is now undergoing change, and the predominant trend of the change is toward greater complexity, which has become known in a collective sense as