Athena Neurosciences F-4 Registration of securities (foreign)

Exhibit 21.1

Organizational Structure

At December 31, 2004, Elan Corporation, plc had the following principal subsidiary undertakings:

Company

Nature of Business

Group Share %

Registered Office & Country of Incorporation & Operation

Athena Neurosciences, Inc.

Holding company

100

800 Gateway Blvd South San Francisco, CA, United States

Elan Capital Corporation, Ltd

Financial services company

100

Clarendon House, 2 Church St Hamilton, Bermuda

Elan Drug Delivery, Inc.

R&D

100

3000 Horizon Drive King of Prussia, PA, United States

Elan Finance, plc

Financial services company

100

Treasury Building, Lower Grand Canal Street, Dublin 2, Ireland

Elan Holdings, Inc.

Manufacture, marketing and distribution of pharmaceutical and medical device products

100

1300 Gould Drive Gainesville, GA, United States

Elan Holdings, Ltd

Holding company

100

Monksland, Athlone Co. Westmeath, Ireland

Elan International Services, Ltd

Financial services company

100

Clarendon House, 2 Church St Hamilton, Bermuda

Elan Management, Ltd

Provision of management services

100

Treasury Building, Lower Grand Canal Street, Dublin 2, Ireland

Elan Pharma, Ltd

Manufacture of pharmaceutical products

100

Monksland, Athlone Co. Westmeath, Ireland

Elan Pharma International, Ltd

R&D, manufacture, sale and distribution of pharmaceutical products and financial services

100

WIL House, Shannon Business Park, Co Clare, Ireland

Elan Pharmaceuticals, Inc.

R&D and sale of pharmaceutical products

100

800 Gateway Blvd South San Francisco, CA, United States

Elan Pharmaceutical Investments, III, Ltd

Investment holding company

100

Clarendon House, 2 Church St Hamilton, Bermuda

Monksland Holdings BV

Financial services company

100

Amsteldijk 166 6th Floor 1079 LH Amsterdam The Netherlands