I have a huge, healthy antique climbing rose- about 10 years old. It is twining through an arbor on the top of my fence. The fence needs to be replaced. How much can I prune back the rosebush without hurting it too much? I plan to wait until after it blooms this spring.

you will need to prune your climber to about 12" canes, and remove all but the best 3 or 4. this will allow the roots to reestablish without having to support too much top growth at the time. i did this with old blush climber. she moved without any problem. it took her two years to get back to a comparable size as before. Focus on the roots. that what will make or break the move.
good luck!
bj

Thanks for the info. I'm not planning to move the rose bush- just cut it back in order to put in a new fence. Does the same advice hold, or can I do a less agressive pruning?

you can absolutely do less pruning. i was thinking you were going to take it out of the ground. you can in fact prune it to whatever you need to. just prune so that the growth that comes from the cut cane is directed up and outward rather than in toward the center of the plant.