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10. McKesson Corporation (MCK)

Contracted in 2011: $4.7 billion
Total 2011 revenue: $112 billion
Contracted in 2012, so far: $2.38 billion
Company Profile

McKesson Corporation, headquartered in San Francisco, Calif., describes itself as a pharmaceutical distributor and health care information technology company.

A majority of the government contracts ($3.8 billion) with the company arose from the department of Veteran Affairs and its top 10 contracts have all been awarded for drugs and biologicals, according to USASpending.gov.

In its 2011 annual report, it notes the significance of government contracts as a key risk factor: “The loss of such contracts could have a material adverse impact on our results of operations.”

Photo: Thomas Tolstrup | Riser | Getty Images