Both perform the same kind of service, yes. If you're using RMI's registry and it's sufficient for what you're doing, probably you don't want to bother with JNDI. It offers more features and greater flexibility but for simple RMI it's far more work to deploy it.
Make visible what, without you, might perhaps never have been seen. - Robert Bresson
JNDI = Java Naming and Directory Interface. it gives you a common access to several naming and directory services. JNDI is built uppon a provider architecture -> you can access every naming service as long as there is a provider for it. There is a wide range available from sun, i think. (RMI registry, LDAP... check the sun page) there are also providers available for other services (you might have to pay) like a windows registry service provider. -> if you just want to do some RMI: go with RMI registry. -> if you develop on RMI regsitry but client might use other (or several other) naming services: go with JNDI -> if you are curious and have enough time: give it a glance. k