The development of the UIUC Virtual Spectrometer (UIUC-VS), an interactive, Java-based simulation and tutoring system, is discussed. The apprenticeship model oflearning is utilized to create a learning environment for the study of a one-dimensional proton nuclear magnetic resonance (NMR) experiment, with the goal of linking theoretical knowledge with practical operational experience. Active, exploratory, apprentice-style learning is supported via modes of operation within the system. Students can flexibly choose to "observe the expert" perform and explain operational steps, or "act as an apprentice" and carry out the steps autonomously. Students can switch between modes at their discretion, giving them control of the level of system intervention. Students can also explore and reflect on an "information space" of objects, procedures, and related concepts. UIUC-VS extends a previous tutorial application, LEMRS, 1 using Java-based, Web-capable technologies to provide a basis for a shared simulation environment teaching NMR. As a computer-supported collaborative learning environment, the system includes a method of asynchronous communication, where the student can post questions and comments to a "question board," with the ability to capture the current state of the system via annotations on a screen capture. Formative evaluations involving undergraduate chemistry students were crucial to system redesign.