Chapman and Cutler LLP
111 West Monroe Street
Chicago, Illinois 60603
October 3, 2017
Mr. Edward Bartz
Division of Investment Management
Securities and Exchange Commission
100 F Street, N.E.
Washington, DC 20549
Re: Guggenheim Defined Portfolios, Series 1678
Convertible & Income Portfolio of Funds, Series 27
File Nos. 333-220192 and 811-03763
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Dear Mr. Bartz:
This letter is in response to your comment given during a telephone
conversation with our office regarding the registration statement on Form S-6
for Guggenheim Defined Portfolios, Series 1678, filed on August 28, 2017, with
the Securities and Exchange Commission (the "Commission"). The registration
statement proposes to offer the Convertible & Income Portfolio of Funds, Series
27 (the "Trust").
PROSPECTUS
Investment Summary -- Principal Risks
1. The duration example in the sixth bullet uses a duration of five
years. Please confirm that the average weighted duration of the fixed-income
securities held indirectly by the Trust is approximately five years or less. If
not, please revise this example to reflect the average weighted duration of the
fixed-income securities.
Response: The sponsor confirm that the average weighted duration of the
fixed-income securities held indirectly by the Trust is approximately five years
or less and, therefore, the example does not need to be revised.
We appreciate your prompt attention to this registration statement. If you
have any questions or comments or would like to discuss our responses to your
questions, please feel free to contact the undersigned at (312) 845-3484.
Very truly yours,
CHAPMAN AND CUTLER LLP
By /s/ Morrison C. Warren
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Morrison C. Warren