Abstract: Dynamic load balancing is a very important problem in distributed processing. This problem aims to redistribute running processes to achieve better results according some optimization criterion. Since it is a NP-Complete problem in its general formulation, it is worth to use heuristics to seek better results in a reasonable time. One of the heuristics that has been successfully applied in various static scheduling problems is genetic algorithms (GSs). In this paper, we propose to use a classifier system that is an adaptive systems that applies a GA over a population of decisions about when to do preemptive migrations in a distributed environment. The results have been impressive and the classifier system was able to surpass, without previous knowledge of the workload, the performance of a well designed analytic criterion.