Quote - depending on what you are trying to sculpt you neeed to add topology to the mesh

in the 2.66 series and after there is a tool called dynamic topology in the sculpt menu on the left

go to sculpt mode and enable dynamic topology under the toplogy tab

you will see a button titled enable dynamic

that will tessalate the mesh only where you tell it to sculpt at

or you could use a subdivision surface modifier

 

Do NOT use dynamic topology if the mesh you're sculpting has UV maps on it already, I'm almost certain it will hose your UVs. I don't have time to test it right now, but generally that kind of change to the geometry is game over for any UV maps you have. The Subidivision Modifier I believe works with UVs, and the "Multiresolution" Modifier I know does, the latter being the most common modifier for sculpting.

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