What is the mortality rate for adults in the USA? 
I'd like to see the number broken down by age groups, if possible. 
A breakdown by cause (accident, cancer, infectious disease, etc) or
gender is not necessary.

I have already found (from the worldbank web site:
http://devdata.worldbank.org/data-query/) that the "crude" rate is 9
per 1000. But this rate is not broken down by age. I would expect the
rate at ages > 65 to be higher than the rate at ages < 65, and for
there to be significant differences by decade...

Dear w0nderd0g,

The most up-to-date publically available data on mortality rates by
age groups in the USA derives from the recently published 2001
National Vital Statistics Report of the US Department of Health and
Human Services, Center for Disease Control and Protection. Here are
the figures:

All death rates are per 100,000 population

Total, all ages ........   848.9
Under 1 year ...........   689.2 
1-4 years ..............    33.4
5-14 years .............    17.3
15-24 years ............    80.5
25-34 years ............   104.7
35-44 years ............   203.2
45-54 years ............   428.3
55-64 years ............   964.1
65-74 years ............  2355.2 
75-84 years ............  5588.2
85 years and over ......15,133.8 
Age-adjusted rate ......   855.0 

You will find addional detailed data, broken down in various ways, in
the 2001 National Vital Statistics Report:
http://www.cdc.gov/nchs/data/nvsr/nvsr51/nvsr51_05.pdf (Acrobat Reader
file!)

Source:

Center for Disease Control and Protection: National Center for Health
Statistics
http://www.cdc.gov/nchs/

Hope this answers your question!
Best regards,
Scriptor

Quick, comprehensive, excellent response. With excellent links,
Thanks!