A typical tennis score is called 'thirty -all' in English (although 'all' seems a bit over the top for singles). In German they would say 'dreissig beider', beider meaning 'both'. How is this score called in French?

I'm going to go out on a limb here...

since fifteen all is quinze-A...I would think that thirty all would be trente-A.

http://french.about.com/library/vocab/sports/bl_tennis.htm

Thanks zbeck.., that seems to answer my question. I've been watching the French Open on TV, and it certainly sounded like trente-A, although my ear wasn't good enough to decide how the 'A' was spelled.
However, ... my french dictionary has only the definition of 'the first letter of the alphabet' for A so what does it mean in the context of tennis scoring? Surely not 'all'?

The umpire is saying "Trente a", which means thirty all. The same applies to quarante a and so on.... Egalite, is when the game is at deuce...

http://www.wikihow.com/Keep-Score-in-Tennis-in-French

The "A" is akin to how it is used in the french version of "all fours" which is "à quatre pattes>"

In French, the scores for fifteen-all, thirty-all and deuce are Quinze-À, Trente-À and Quarante-À. These are simply abbreviations for Quinze-à-quinze, trente-à-trente and quarante-à-quarante.

The first "Deuce" in a game is called by the umpire as "Quarante-À". (Forty-all)

"Égalité" is called for the second and any subsequent "Deuce" scores in the game, i.e if the score returns to “Deuce” from “Advantage”.