EXHIBIT 5


                         [BARNES & THORNBURG LETTERHEAD]




                                                                 August 11, 2003



Vectren Corporation
20 N.W. Fourth Street
Evansville, IN 47708

Ladies and Gentlemen:

     You  have  requested  our  opinion  in  connection  with  the  Registration
Statement on Form S-3 (No. 333-104186) of Vectren Corporation ("Vectren"), filed
pursuant to the  Securities  Act of 1933,  as amended  (the  "Securities  Act"),
relating to the offer and sale by Vectren of up to $150,000,000 of shares of its
common stock,  without par value,  and related common stock purchase rights (the
"Shares"),  and in connection with the  Registration  Statement on Form S-3 (No.
333-107515)  of Vectren filed pursuant to the  Securities  Act,  relating to the
registration  of  up  to  an  additional  $30,000,000  of  Shares  (registration
statement No. 333-104186, including amendments, incorporated documents, exhibits
and financial statements in the form in which such registration statement became
effective on June 27, 2003 and registration statement No. 333-107515 in the form
in which such  registration  statement became effective July 31, 2003 are herein
referred to collectively as the "Registration Statement"), to be issued and sold
under the  provisions of the  Prospectus  dated July 24, 2003 and the Prospectus
Supplement  dated August 7, 2003 (together,  the  "Prospectus")  relating to the
Registration Statement and the Underwriting Agreement, dated August 7, 2003 (the
"Underwriting Agreement", between Vectren and Goldman, Sachs & Co., on behalf of
the  several  Underwriters  named in  Schedule I to the  Underwriting  Agreement
(collectively, the "Underwriters").  We have examined such records, certificates
and other  documents and have made such  investigation  of law as we have deemed
necessary in the circumstances.

     Based on that examination and investigation, it is our opinion that:

     When (i) the Shares are issued and  delivered  by Vectren  pursuant  to the
Underwriting  Agreement  against payment of the  consideration  set forth in the
Underwriting  Agreement,  and (ii)  applicable  state  blue sky laws  have  been
complied  with in connection  with the offer and sale of the Shares,  the Shares
will be validly issued, fully paid and nonassessable.

     This  opinion  letter is limited to the current  Federal laws of the United
States and the current  internal  laws of the State of Indiana  (without  giving
effect to any conflict of law  principles  thereof) and we have not  considered,
and express no opinion on, the laws of any other jurisdiction.

     We consent to the use of our name under the caption "Legal  Matters" in the
Prospectus  Supplement  and to the filing of this  opinion as Exhibit 5.1 to the
Form 8-K of Vectren  filed with the  Securities  and Exchange  Commission on the
date hereof.

                                             Very truly yours,

                                             /s/ Barnes & Thornburg

                                             BARNES & THORNBURG