An A320 flight crew and ZAU ARTCC have confusion about what altitude the aircraft was cleared to.

Attributes
ACN	524800
Time
Date	200109
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	intersection : teddy
State Reference	IL
Altitude	msl bound lower : 11000 msl bound upper : 13000
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	A320
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 13000 flight time type : 1354
ASRS Report	524800
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far
Resolutory Action	controller : issued advisory
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

Descending to cross teddy at 11000 ft, ZAU questioned cleared altitude. We told 11000 ft. He thought we had been cleared to 13000 ft. We leveled at 11000 ft and were given vectors for traffic. When we asked later, the controller was not sure who was at fault. We were sure he had given us 11000 ft, but he was pretty sure he gave us 13000 ft. He said it was no problem. It was at a time he was just starting to put people into hold at teddy including ourselves. He had given us 13000 ft at one time, but then cleared us to 11000 ft later.

Original NASA ASRS Text

Title: AN A320 FLT CREW AND ZAU ARTCC HAVE CONFUSION ABOUT WHAT ALT THE ACFT WAS CLRED TO.

Narrative: DSNDING TO CROSS TEDDY AT 11000 FT, ZAU QUESTIONED CLRED ALT. WE TOLD 11000 FT. HE THOUGHT WE HAD BEEN CLRED TO 13000 FT. WE LEVELED AT 11000 FT AND WERE GIVEN VECTORS FOR TFC. WHEN WE ASKED LATER, THE CTLR WAS NOT SURE WHO WAS AT FAULT. WE WERE SURE HE HAD GIVEN US 11000 FT, BUT HE WAS PRETTY SURE HE GAVE US 13000 FT. HE SAID IT WAS NO PROB. IT WAS AT A TIME HE WAS JUST STARTING TO PUT PEOPLE INTO HOLD AT TEDDY INCLUDING OURSELVES. HE HAD GIVEN US 13000 FT AT ONE TIME, BUT THEN CLRED US TO 11000 FT LATER.

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.