Certification Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
 (subsections (a) and (b) of section 1350, chapter 63 of title 18,
 United States Code)


In connection with the attached Report of Thornburg New York Intermediate
Municipal Fund (a series of Thornburg Investment Trust (the "Trust") on Form
N-CSR to be filed with the Securities and Exchange Commission (the "Report"),
each of the undersigned officers of the Trust does hereby certify that, to the
best of such officer's knowledge:


1. The Report fully complies with the requirements of 13(a) or 15(d) of the
Securities Exchange Act of 1934; and


2. The information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of Thornburg New
York Intermediate Municipal Fund as of, and for, the periods presented in the
Report.


Dated: August 25, 2003


/s/  Brian J. McMahon


Brian J. McMahon


President and principal executive officer


Dated: August 22, 2003


/s/  Steven J. Bohlin


Steven J. Bohlin


Treasurer and chief financial officer


A signed original of this written statement required by Section 906, or other
document authenticating, acknowledging, or otherwise adopting the signature that
appears in typed form within the electronic version of this written statement
required by Section 906, has been provided to the Trust and will be retained by
the Trust and furnished to the Securities and Exchange Commission or its staff
upon request.