Scheduling can be divided into two classes, viz. predictive and reactive scheduling. Predictive scheduling addresses problems with deterministic process times and machine availability and generates a solution valid for the entire time span specified. Reactive scheduling, on the other hand, deals with the problem of maintaining schedules in a dynamic environment such as processing delays, machine breakdown, etc. In this paper a review of the research on scheduling in a dynamic environment is presented. Scheduling approaches have been classified into three categories, viz. conventional, knowledge-based and distributed problem solving. © 1993.