[LETTERHEAD OF THELEN, MARRIN, JOHNSON & BRIDGES LLP]
                                
                                
                              February 20, 1998


Advanced Energy Industries, Inc.
1625 Sharp Point Drive
Fort Collins, CO  80525


Ladies and Gentlemen:

          We have acted as counsel for Advanced Energy
Industries, Inc., a Delaware corporation (the "Company"), in
connection with the preparation of the Registration Statement on
Form S-8 relating to the issuance and sale of shares of common
stock, $0.001 par value, of the Company ("Common Stock") pursuant
to the Company's 1995 Non-Employee Directors Stock Option Plan
(the "Plan")

          Please be advised that we are of the opinion that the
Common Stock to be offered and sold by the Company, when issued
in the manner contemplated by the Plan, will be legally issued,
fully paid and non-assessable.

          We hereby consent to the filing of this opinion with
the Commission as an exhibit to the Registration Statement on
Form S-8.  Except as stated above, without our prior written
consent, this opinion may not be furnished or quoted to any other
person or entity for any purpose.

                        Very truly yours,
                                
             /s/THELEN, MARRIN, JOHNSON & BRIDGES LLP
                                
              THELEN, MARRIN, JOHNSON & BRIDGES LLP


JLM/MLJ