Narrative:

I was cleared down to 10000 ft MSL from 12000 ft MSL and descended through 10000 ft MSL to 9700 ft MSL. My clearance for flight was cid direct bbw at 12000 ft MSL. Solution: be more attentive to altimeter during descent when given altitude to descend to.

Google
 

Original NASA ASRS Text

Title: PLT OF A C182RG ON AN IFR XCOUNTRY FLT OVERSHOT DSCNT ALT AND CORRECTED BACK.

Narrative: I WAS CLRED DOWN TO 10000 FT MSL FROM 12000 FT MSL AND DSNDED THROUGH 10000 FT MSL TO 9700 FT MSL. MY CLRNC FOR FLT WAS CID DIRECT BBW AT 12000 FT MSL. SOLUTION: BE MORE ATTENTIVE TO ALTIMETER DURING DSCNT WHEN GIVEN ALT TO DSND TO.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.