Exhibit 5
                                                                       ---------
                         NUTTER, McCLENNEN & FISH, LLP

                               ATTORNEYS AT LAW

                            ONE INTERNATIONAL PLACE
                       BOSTON, MASSACHUSETTS  02110-2699

          TELEPHONE:  617-439-2000          FACSIMILE:  617-973-9748

CAPE COD OFFICE                                               DIRECT DIAL NUMBER
HYANNIS, MASSACHUSETTS


                                 June 18, 1999


Nabi
5800 Park of Commerce Boulevard, N.W.
Boca Raton, FL  33487

Gentlemen/Ladies:

         Reference is made to the registration statement on Form S-8 (the
"Registration Statement") which Nabi (the "Company") is filing concurrently
herewith with the Securities and Exchange Commission under the Securities Act of
1933, as amended (the "Securities Act"), with respect to 150,000 shares of the
Company's common stock, $0.10 par value per share (the "Common Stock"), issuable
pursuant to the Company's Stock Plan for Non-Employee Directors, as amended to
date (the "Plan"), and an indeterminate number of shares of such Common Stock
which may be issued or become issuable under the Plan by reason of stock
dividends, stock splits or other recapitalizations executed hereafter.

         We have acted as legal counsel for the Company in connection with the
creation of and amendments to the Plan, are familiar with the Company's Amended
and Restated Certificate of Incorporation and By-laws, both as amended to date
(collectively, the "Organizational Documents"), and have examined such other
documents as we deemed necessary for this opinion.  Based upon the foregoing, we
are of the opinion that:

         1.   When issued and paid for in compliance with the terms of the Plan,
the Organizational Documents and the Delaware General Corporation Law, the
150,000 shares of Common Stock referred to above will be duly and validly
issued, fully paid and non-assessable; and

         2.   The additional shares of Common Stock which may become issuable
under the Plan by reason of stock dividends, stock splits or other
recapitalizations hereafter executed, if and when issued in accordance with the
terms of the Plan and upon compliance with the applicable provisions of law and
of the Organizational Documents, will be duly and validly issued, fully paid and
non-assessable.

    We understand that this opinion letter is to be used in connection with the
Registration Statement and hereby consent to the filing of this opinion letter
with and as a part of the Registration Statement and of any amendments thereto.
It is understood that this opinion letter is to be used in connection with the
offer and sale of the aforesaid shares only while the Registration Statement, as
it may be amended from time to time as contemplated by Section 10(a)(3) of the
Securities Act, is effective under the Securities Act.

                             Very truly yours,

                             /s/ Nutter, McClennen & Fish, LLP

                             Nutter, McClennen & Fish, LLP