Intangible Assets

Intangible assets consisted of:



	March 31, 2019				September 30, 2018
(Millions of dollars)	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Amortized intangible assets
Developed technology	$	13,976	$	2,352	$	13,966	$	1,782
Customer relationships	4,586		1,022		4,584		861
Product rights	118		60		121		58
Trademarks	407		93		407		84
Patents and other	407		295		397		288
Amortized intangible assets	$	19,495	$	3,822	$	19,475	$	3,073
Unamortized intangible assets
Acquired in-process research and development	$	31			$	37
Trademarks	2				2
Unamortized intangible assets	$	33			$	39

Intangible amortization expense for the three months ended March 31, 2019 and 2018 was $376 million and $370 million, respectively. Intangible amortization expense for the six months ended March 31, 2019 and 2018 was $754 million and $505 million, respectively. The increase in intangible amortization expense for the six months ended March 31, 2019 was attributable to assets acquired in the Bard transaction, which is further discussed in Note 9.

The following is a reconciliation of goodwill by business segment:



(Millions of dollars)	Medical			Life Sciences			Interventional			Total
Goodwill as of September 30, 2018	$	10,054		$	775		$	12,771		$	23,600
Divestiture-related adjustments	—			3			—			3
Purchase accounting adjustments (a)	(15		)	—			(70		)	(84		)
Currency translation	(3		)	(2		)	—			(5		)
Goodwill as of March 31, 2019	$	10,036		$	776		$	12,701		$	23,513


(a)	The purchase accounting adjustments were primarily driven by adjustments to tax-related balances.