<page>									  EXHIBIT 31.01

CERTIFICATIONS

I, Jeffrey A. Rothman, President of Demeter Management Corporation
(?Demeter?), the general partner of the registrant, Dean Witter
Principal Plus Fund L.P., certify that:

1.	I have reviewed this quarterly report on Form 10-Q of the
registrant;

2.	Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the
circumstances under which such statements were made, not
misleading with respect to the period covered by this report;

3.	Based on my knowledge, the financial statements, and other
financial information included in this report, fairly present in
all material respects the financial condition, results of
operations, and cash flows of the registrant as of, and for, the
periods presented in this report;

4.	The registrant?s other certifying officer and I are responsible
for establishing and maintaining disclosure controls and
procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-
15(e)) and internal control over financial reporting (as defined
in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the
registrant and have:

a)	Designed such disclosure controls and procedures, or caused
such disclosure controls and procedures to be designed under
our supervision, to ensure that material information
relating to the registrant, including its consolidated
subsidiaries, is made known to us by other within those
entities, particularly during the period in which this
report is being prepared;

     b) Designed such internal control over financial reporting, or
caused such internal control over financial reporting to be
designed under our supervision, to provide reasonable
assurance regarding the reliability of financial reporting
and the preparation of financial statements for external
purposes in accordance with generally accepted accounting
principles;

     c) Evaluated the effectiveness of the registrant?s disclosure
controls and procedures and presented in this report our
conclusions about the effectiveness of the disclosure <page>
controls and procedures, as of the end of the period covered
by this report based on such evaluation; and

     d) Disclosed in this report any change in the registrant?s
internal control over financial reporting that occurred
during the registrant?s most recent fiscal quarter (the
registrant?s fourth fiscal quarter in the case of an annual
report) that has materially affected, or is reasonably likely
to materially affect, the registrant?s internal control over
financial reporting; and

5.	The registrant?s other certifying officer and I have disclosed,
based on our most recent evaluation of internal control over
financial reporting, to the registrant?s auditors and the audit
committee of Demeter?s board of directors (or persons performing
the equivalent functions):

a)	All significant deficiencies and material weaknesses in the
design or operation of internal control over financial
reporting which are reasonably likely to adversely affect the
registrant?s ability to record, process, summarize, and
report financial information; and

b)	Any fraud, whether or not material, that involves management
or other employees who have a significant role in the
registrant?s internal control over financial reporting.




Date:   August 15, 2005    /s/Jeffrey A. Rothman
                              Jeffrey A. Rothman
                              President,
                              Demeter Management Corporation,
                              general partner of the registrant