JETNET 3.0 is a F77 subroutine package and contains a number of subroutines that are called from a main program written by the user. JETNET 3.0 is divided in two parts, one for feed-forward back-propagation networks and another for self-organizing maps. The subroutines associated with the feed-forward net all begin with the letters JN, as in JetNet, whereas the self-organizing map subroutines all start with JM, as in JetMap. We will not discuss any of the JetMap subroutines and components here since they are basically unchanged from JETNET 2.0 . JETNET 3.0 is backwards compatible with earlier versions.