In literature, several cases are reported of models of discrete non-stochastic production systems that show irregular, apparently chaotic behavior. In this paper a number of these cases are analyzed, and the irregular behavior is attributed to (1) chaotic behavior in hybrid models, (2) chaotic behavior in discrete-event models that use a chaotic map, or (3)periodic behavior with a period longer than the observation window. The irregular behavior of a discrete-event model of a two-machine productionsystem is analyzed by means of nonlinear time series analysis and sensitivity analysis. This case reveals the possibilities and limitations of the application of chaos theory to discrete-event models of productionsystems. Also, a new method for determining the sensitivity of discrete-event models to truly small changes is introduced. Realistic, non-artificial discrete-event models of discrete production systems that show chaotic behavior were not found in this study.