Exhibit 21.1

SUBSIDIARIES OF REGISTRANT
AS OF OCTOBER 31, 2010

ABM INDUSTRIES INCORPORATED

(*) ABM Facility Services Company

ABM Engineering Services Company

ABM Security Services, Inc.

SSA Security, Inc.

Elite Security, Inc.

Ampco System Parking

Ampco-M***

Ampco Pacific Airpark, LLC***

Pansini Oakland Associates, LP***

American Public Services

ATL and Electrical Services

ATL Services

ATL Services of the Midwest

ABM Janitorial Services, Inc.

ABM Janitorial Services — Mid-Atlantic, Inc.

ABM Janitorial Services — North Central, Inc.

ABM Janitorial Services — Northeast, Inc.

ABM Janitorial Services — Northern California

ABM Janitorial Services — Northwest, Inc.

ABM Janitorial Services — South Central, Inc.

ABM Janitorial Services — Southeast, LLC

ABM Janitorial Services — Southwest, Inc.

ABM Government Services, Inc.

American Building Maintenance Co. of Hawaii

Allied Maintenance Services, Inc.

ABM Janitorial Services Co., Ltd.

Canadian Building Maintenance Company, Ltd.

Supreme Building Maintenance, Ltd.

Diversco, Inc.

OneSource Holdings, LLC

OneSource Facility Services, LLC

ABM Janitorial Services — Midwest, LLC

OneSource Servicos de Mexico S.A. de C.V.

FCI Servicos de Mexico S.A. de C.V.

FCI Servisitema S.A. de C.V.

OneSource Painting, Inc.**

OneSource Property Holdings, Inc.**

OneSource Landscape & Golf Services, Inc.

Servall Services, Inc.

SM Newco Corp.

Southern Management

ABM Shared Services, Inc.

Amtech Energy Services**

Amtech Reliable Elevator Company of Texas**

OneSource Services, LLC

*	Subsidiary relationship to Company or to subsidiary parents shown by progressive indentation.
**	Inactive companies
***	Limited Partnership