Abstract: A system and method for run time configuration of objects within an object oriented computing environment permits class substitution, instance redirection and class redirection at run time. Class redirection permits class message calls to be redirected from a first class to a second class at run time. In class redirection, the second class uses all new instances of the first class. Instance redirection enables both class messages and instance messages to be redirected from the first class to the second class of run time. In instance redirection, the second class uses all new and existing instances of the first class. Class substitution enables both class messages and instance messages to be redirected and also enables insertion of a new class into the class hierarchy at run time. In class substitution, the second class uses all new instances and existing instances of the first class and all new instances and existing instances of the descendants of the first class.