Current literature motivates development of a general, WWW-based simulation package with maximum user interactivity and cross-platform capabilities. Netsim, a general, WWW-based, discrete-event simulation package written entirely in Java, meets this need. Java is an object-oriented programming language designed for internet programming. It makes Netsim possible and enables easy incorporation with existing WWW materials. As a result, Netsim supports and enhances the existing WWW environment for users of all levels. Netsim provides complete model creation and modification capabilities, through the event graph paradigm, along with both graphical animation and data output. Netsim allows expandability for complex modeling and integration with other Java-based programs and future extensions. Scope and purpose Research in the area of World Wide Web-based simulation is growing rapidly as World Wide Web (WWW) programming tools develop. Still, much of this research provides only limited, WWW-based simulation capabilities. Netsim answers these limitations and provides a positive, unique contribution to WWW-based simulation by combining Java, event graphs, and the WWW into a general simulation package. In particular, Netsim (1) provides a simple method for including interactive, discrete-event simulation in WWW sites, (2) uses graphical interfaces for model entry, editing and manipulation, (3) allows user control of model execution, (4) provides animated and numerical output, (5) uses Java to provide: (i) object oriented flexibility which: (a) allows straightforward code modification and re-use, (b) minimizes computer memory usage, (c) allows easy program expansion; (ii) platform independence through the WWW; (iii) compatibility with other Java-based graphical and analytical tools, and (6) does not require external applications or databases. By accessing Netsim simulation models through the WWW, users are able to ensure a common reference and to easily communicate, building on understandings and ideas. Additionally, through animation and data output, Netsim contributes a graphic as well as analytic representation of a system process. This enables users to understand the system both visually and statistically.