https://secure.wikimedia.org/wikipedia/en/wiki/Doctor_%28title%29#United_States https://secure.wikimedia.org/wikipedia/en/wiki/Doctor_%28tit... This wikipedia

https://secure.wikimedia.org/wikipedia/en/wiki/Doctor_%28title%29#United_States https://secure.wikimedia.org/wikipedia/en/wiki/Doctor_%28tit... This wikipedia entry seems to indicate that it is common to address someone of his stature as "Dr.", with the possible exception of perhaps in social settings where doing so might cause confusion (with MD).