REPORT OF INDEPENDENT REGISTERED PUBLIC
ACCOUNTING FIRM

To the Board of Trustees and Shareholders of Tekla Life
Sciences Investors

In planning and performing our audit of the financial
statements of Tekla Life Sciences Investors (the "Fund")
as of and for the year ended September 30, 2018, in
accordance with the standards of the Public Company
Accounting Oversight Board (United States) (PCAOB),
we considered the Fund's internal control over financial
reporting, including controls over safeguarding
securities, as a basis for designing our auditing
procedures for the purpose of expressing our opinion
on the financial statements and to comply with the
requirements of Form N-CEN, but not for the purpose of
expressing an opinion on the effectiveness of the Fund's
internal control over financial reporting. Accordingly,
we express no such opinion.

The management of the Fund is responsible for
establishing and maintaining effective internal control
over financial reporting. In fulfilling this responsibility,
estimates and judgments by management are required
to assess the expected benefits and related costs of
controls. A fund's internal control over financial
reporting is a process designed 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. A fund's internal control over
financial reporting includes those policies and
procedures that (1) pertain to the maintenance of
records that, in reasonable detail, accurately and fairly
reflect the transactions and dispositions of the assets of
the fund; (2) provide reasonable assurance that
transactions are recorded as necessary to permit
preparation of financial statements in accordance with
generally accepted accounting principles, and that
receipts and expenditures of the fund are being made
only in accordance with authorizations of management
and trustees of the fund; and (3) provide reasonable
assurance regarding prevention or timely detection of
unauthorized acquisition, use, or disposition of a fund's
assets that could have a material effect on the financial
statements.

Because of its inherent limitations, internal control over
financial reporting may not prevent or detect
misstatements. Also, projections of any evaluation of
effectiveness to future periods are subject to the risk
that controls may become inadequate because of
changes in conditions or that the degree of compliance
with the policies or procedures may deteriorate.

A deficiency in internal control over financial reporting
exists when the design or operation of a control does
not allow management or employees, in the normal
course of performing their assigned functions, to
prevent or detect misstatements on a timely basis. A
material weakness is a deficiency, or a combination of
deficiencies, in internal control over financial reporting,
such that there is a reasonable possibility that a
material misstatement of a fund's annual or interim
financial statements will not be prevented or detected
on a timely basis.

Our consideration of the Fund's internal control over
financial reporting was for the limited purpose
described in the first paragraph and would not
necessarily disclose all deficiencies in internal control
that might be material weaknesses under standards
established by the PCAOB. However, we noted no
deficiencies in the Fund's internal control over financial
reporting and its operation, including controls for
safeguarding securities that we consider to be a
material weakness, as defined above, as of September
30, 2018.

This report is intended solely for the information and
use of management and the Board of Trustees of the
Fund and the Securities and Exchange Commission and
is not intended to be and should not be used by anyone
other than these specified parties.

/s/ DELOITTE & TOUCHE LLP

Boston, Massachusetts

November 20, 2018