Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2011

Retirement Benefits

Schedule of Defined Benefit Plans Disclosures

	Pension Benefits(a)												Postretirement Benefits(a)
	Three Months						Six Months						Three Months						Six Months
	2011			2010			2011			2010			2011			2010			2011			2010
Service cost	$	18		$	16		$	38		$	33		$	5		$	5		$	11		$	10
Interest cost		45			46			90			93			14			14			29			30
Expected return on plan assets		(54	)		(53	)		(108	)		(106	)		(13	)		(14	)		(27	)		(28	)
Amortization of:
Transition obligation		-			-			-			-			1			1			1			1
Prior service cost (benefit)		(1	)		2			(1	)		4			(2	)		(2	)		(4	)		(4	)
Actuarial loss (gain)		10			4			21			9			1			(1	)		2			1
Net periodic cost	$	18		$	15		$	40		$	33		$	6		$	3		$	12		$	10

(a) Includes amounts for Ameren registrant and nonregistrant subsidiaries.

Schedule Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans by Company

	Pension Costs								Postretirement Costs
	Three Months				Six Months				Three Months				Six Months
	2011		2010		2011		2010		2011		2010		2011		2010
Ameren Missouri	$	12	$	9	$	26	$	21	$	2	$	2	$	5	$	5
Ameren Illinois		3		4		8		6		4		1		6		4
Genco		3		2		5		5		-		-		1		1
Other		-		-		1		1		-		-		-		-
Ameren(a)	$	18	$	15	$	40	$	33	$	6	$	3	$	12	$	10

(a) Includes amounts for Ameren registrant and nonregistrant subsidiaries.