For many people, a key form of learning how to use software, for example, is not by taking a training course, nor reading a manual or online help, or experimenting with the software. Instead they may lean over the shoulder of a colleague at work and ask for help. This over-the-shoulder-learning (OTSL) is important to study to understand more about its relative importance and the circumstances in which it is and is not successful. Building on prior work studying informal collaborative help in libraries and offices, the research will address how often OTSL occurs and its significance as a way of learning, possible genres of OTSL, the evolution of learning a software application over time, the resources people use to support OTSL, barriers to OTSL as currently practiced, and the skills of efficient help-giving and determining how these skills may best be taught. This work will help determine the functionalities that have the greatest potential for improving the effectiveness of OTSL and contribute to fundamental research in user interface design and computer-supported cooperative work and learning.