County Index - Co Londonderry
- 1ST Class Blinds - Co Londonderry - Limavady
- 3 P S Computer Services - Co Londonderry - Limavady
- 3d Limos - Co Londonderry - Londonderry
- 3JM Fencing Supplies - Co Londonderry - Maghera
- 4d Productions Ltd - Co Londonderry - Coleraine
- 4sythe 4sewing - Co Londonderry - Magherafelt
- @capaa - Co Londonderry - Maghera
- A B A Developments - Co Londonderry - Londonderry
- A D Surveyors Ltd - Co Londonderry - Magherafelt
- A D Canning - Co Londonderry - Londonderry
- A Diamond & Son (Timber) Ltd. - Co Londonderry - Coleraine
- A E McCandless & Co. Ltd. - Co Londonderry - Londonderry
- A Gillan - Co Londonderry - Coleraine
- A H Fuel Oils Ltd - Co Londonderry - Portstewart
- A J C Lamont (Trailers) - Co Londonderry - Coleraine
- A J Christie - Co Londonderry - Londonderry
- A McCann - Co Londonderry - Londonderry
- A P Equipment(N I) Ltd. - Co Londonderry - Magherafelt
- A Q B Architectural Workshop Ltd - Co Londonderry - Londonderry
- A Q B Architectural Workshop - Co Londonderry - Londonderry
- A S I - Co Londonderry - Londonderry
- A S I Architects Ltd - Co Londonderry - Londonderry
- A T G Services (Ireland) Ltd - Co Londonderry - Coleraine
- A T R Superfreeze Refrigeration - Co Londonderry - Magherafelt
- A. Conway & Co Ltd - Co Londonderry - Londonderry
- A. McLean Ltd - Co Londonderry - Limavady
- A.J. Armstrong & Sons Ltd - Co Londonderry - Maghera
- A1 Coach Travel Ltd - Co Londonderry - Londonderry
- A1 Embroidery - Co Londonderry - Maghera
- A1 Speediprint Ltd - Co Londonderry - Londonderry
- Ab Computers - Co Londonderry - Londonderry
- Abbey Rewind - Co Londonderry - Coleraine
- Acorn It Computers Ltd - Co Londonderry - Maghera
- Acorn It Solutions - Co Londonderry - Maghera
- Active Alarms - Co Londonderry - Londonderry
- Af Joinery Ltd. - Co Londonderry - Limavady
- Aghadowey Creamery Ltd - Co Londonderry - Coleraine
- Agrapork - Co Londonderry - Magherafelt
- Agri-Fab Engineering - Co Londonderry - Magherafelt
- Agrispares (N I) Ltd. - Co Londonderry - Londonderry
- Air Cool Engineering (NI) Ltd - Co Londonderry - Limavady
- Air products Plc t/a Allgo Mechanical Engineering Ltd - Co Londonderry - Londonderry
- Ajm Machine Repairs Ltd - Co Londonderry - Coleraine
- Alan McGarrigle Signs - Co Londonderry - Londonderry
- Alastair's Home Bakery - Co Londonderry - Magherafelt
- All Pipe Engineering Ltd. - Co Londonderry - Londonderry
- All Sewn Up - Co Londonderry - Limavady
- Allersafe Ltd - Co Londonderry - Coleraine
- Allgo Engineering Supplies Ltd - Co Londonderry - Londonderry
- Alphatec Wiring Systems - Co Londonderry - Londonderry
- AME Electrical - Co Londonderry - Maghera
- Analogue & Digital Services - Co Londonderry - Limavady
- Anderson Banners - Co Londonderry - Coleraine
- Anthony O'Neill - Co Londonderry - Magherafelt
- Aquaholics - Co Londonderry - Portstewart
- Archie O'Kane - Co Londonderry - Maghera
- Ardmore (Co. Derry) Pre-Cast Concrete Ltd. - Co Londonderry - Londonderry
- Arm Fire & Security Ltd - Co Londonderry - Limavady
- Armour Trailers & Engineering - Co Londonderry - Magherafelt
- Armstrong Joinery & Timber Merchants Ltd - Co Londonderry - Coleraine
- Armstrong Medical Ltd. - Co Londonderry - Coleraine
- Arrell Engineering - Co Londonderry - Magherafelt
- Art Glass - Co Londonderry - Londonderry
- Art Glass (N.I.) Ltd - Co Londonderry - Londonderry
- Asbestos Management Company (Ireland) Ltd - Co Londonderry - Coleraine
- Ashland Chemicals & Hygiene Supplies Ltd. - Co Londonderry - Limavady
- Asphalt Burner Services - Co Londonderry - Magherafelt
- Atcheson & Son (Derry) Ltd - Co Londonderry - Londonderry
- Atp Architects Ltd - Co Londonderry - Coleraine
- Auto Care Products N I - Co Londonderry - Coleraine
- Avaunt It Solutions - Co Londonderry - Londonderry
- B Mullan & Sons (Contractors) Ltd. - Co Londonderry - Limavady
- B H P Alarms Ltd. - Co Londonderry - Londonderry
- B M Groundworks Ltd. - Co Londonderry - Londonderry
- B P McKeefry Ltd - Co Londonderry - Maghera
- B.M.K. Steel Ltd - Co Londonderry - Magherafelt
- Ballyarnett Racecourse Preservation Society - Co Londonderry - Londonderry
- Ballywilliam Properties Ltd - Co Londonderry - Coleraine
- Bann Building Co - Co Londonderry - Coleraine
- Bann Engineering Co. Ltd. - Co Londonderry - Coleraine
- Bap Express Foodservice Ltd - Co Londonderry - Londonderry
- Bearna Solutions Ltd - Co Londonderry - Magherafelt
- Beech-Hill Stables - Co Londonderry - Magherafelt
- Bellarena Fuels Ltd - Co Londonderry - Limavady
- Bells of Cappagh Ltd. - Co Londonderry - Portstewart
- Bentley Instrument Co. Ltd. - Co Londonderry - Londonderry
- Bertie Montgomery - Co Londonderry - Magherafelt
- Betteronics Ltd - Co Londonderry - Londonderry
- Betty McCloskey - Co Londonderry - Londonderry
- Biofoss Renewables Ltd - Co Londonderry - Maghera
- Bishops Ironics - Co Londonderry - Limavady
- Blackhill Construction Ltd - Co Londonderry - Londonderry
- Blaney Gears Ltd - Co Londonderry - Limavady
- Blaney Gears Ltd - Co Londonderry - Limavady
- Bob Jefferson - Co Londonderry - Coleraine
- Bolton Farms - Co Londonderry - Magherafelt
- Box Displays - Co Londonderry - Limavady
- BP McKeefry Holdings Ltd - Co Londonderry - Maghera
- Bradley C - Co Londonderry - Coleraine
- Brennan Associates - Co Londonderry - Londonderry
- Brennen Associates - Co Londonderry - Coleraine
- Brian Baird Achitect - Co Londonderry - Coleraine
- Brian Brolly - Co Londonderry - Londonderry