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Exhibit 21

LIST OF SUBSIDIARIES

Registrant - National Service Industries, Inc.

Registrant owns, directly or indirectly, all of the common stock of the
following subsidiaries:

State or Other
Jurisdiction
of Incorporation
Subsidiary Principal Location or Organization
- ----------------------------------------- ----------------------- ----------------

Chemical Continental Industries S.A.R.L. Nogent-le-Roi, France France
Chemical Specialties B.V. Bergen op Zoom, Holland Netherlands
Graham International B.V. Bergen op Zoom, Holland Netherlands
Kem Europa B.V. Bergen op Zoom, Holland Netherlands
Keplime B.V. Bergen op Zoom, Holland Netherlands
Lithonia Lighting Mexico, S.A. de C.V. Monterrey, Nuevo Leon Mexico
Lithonia Lighting Servicios, S.A. de C.V. Monterrey, Nuevo Leon Mexico
National Service Industries, Inc. Atlanta, Georgia Georgia
NSI Enterprises, Inc. Atlanta, Georgia California
NSI Holdings, Inc. Montreal, Quebec, Canada Canada
NSI Insurance (Bermuda) Ltd. Hamilton, Bermuda Bermuda
NSI Leasing, Inc. Atlanta, Georgia Delaware
Productos Lithonia Lighting de Mexico, S.A. de C.V. Monterrey, Nuevo Leon Mexico
Research Development Industries S.A. Nogent-le-Roi, France France
Resolve S.A. Nogent-le-Roi, France France
Selig Company of Puerto Rico, Inc. Atlanta, Georgia Puerto Rico
ZEP Belgium S.A. Brussels, Belgium Belgium
ZEP Europe B.V. Bergen op Zoom, Holland Netherlands
ZEP FRANCE Nogent-le-Roi, France France
Zep Industries S.A. Nogent-le-Roi, France France
Zep Italia S.r.l. Aprilia, Italy Italy
Zep Manufacturing B.V. Bergen op Zoom, Holland Netherlands
Zep Manufacturing Company Santa Clara, California Delaware
Zep S.A. Bern, Switzerland Switzerland

The consolidated financial statements include the accounts of all subsidiaries.