Spell Resistance

[Ralcos]

I have a character idea that gains spell resistance (A drow with the half-fiend template) from two different sources.
From the Drow, I'd gain 11 + class levels in SR.
From the Half-Fiend, I'd gain 10 + HD in SR.

How would I calculate SR from this combination? Do they stack? Do I just get the highest?

[FullStop]

I have a character idea that gains spell resistance (A drow with the half-fiend template) from two different sources.
From the Drow, I'd gain 11 + class levels in SR.
From the Half-Fiend, I'd gain 10 + HD in SR.

How would I calculate SR from this combination? Do they stack? Do I just get the highest?

Inclined to say it's the latter.

[Arael666]

As the SRD states:

Spell resistance does not stack. It overlaps. (http://www.d20srd.org/srd/specialAbilities.htm)

[fishyfishyfishy]

As was stated, you do not get the benefit of both. In order to avoid massive LA and redundancy I suggest you use the Lesser Drow variant.

[Kazudo]

It's treated pretty much the same as DR. DR from different sources overlaps unless it says it stacks, which is RARE.