| Agence Markel | Longueuil | Computer Networking |
| Agence PID | Longueuil | Clothes Lines |
| Agropur | Longueuil | Agri-food, Cheese |
| Ah Mi Ma So | Longueuil | so |
| Air Péloquin Inc. | Longueuil | Tout Entreprises et services |
| Airco Den Bec | Longueuil | Air Conditioning Systems & Parts |
| Airgel Inc | Longueuil | Air Conditioning Contractors |
| Airmec Climatisation | Longueuil | Air Conditioning Contractors |
| Airomax | Longueuil | Tout Entreprises et services |
| Airteck Propulsion | Longueuil | Air Conditioning Contractors |
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| Akilon Technologies Inc | Longueuil | Computer Networking |
| Alain Berthiaume CPA Inc | Longueuil | Bookkeeping Software & Accounting Systems |
| Alcius | Longueuil | Advertising Agencies |
| Alea Coiffure Inc | Longueuil | Beauty & Fitness, Hairdressers & Beauty Salons |
| Alejandra Ibarra Acupuncture | Longueuil | Acupuncturists |
| Alexandre Germain | Longueuil | Business Lawyers |
| Alia N Tangay | Longueuil | Clothing Stores |
| Alimentation Raymond Drouin Inc | Longueuil | Not Profit, Grocery Stores |
| Aliments du Québec | Longueuil | Tout Commerces au détail, Tout Entreprises et services |
| Aliments Krispy Kernels Inc | Longueuil | Chips |
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| Aliments Krispy Kernels Inc. | Longueuil | Agri-food |
| Aliments Ultima | Longueuil | Agri-food |
| Aliments Ultima Inc | Longueuil | Agri-food |
| Alliance Santé Soutien a Domicile | Longueuil | Care Homes |
| alterfina | Longueuil | Tout Entreprises et services |
| Aluminium Alouette Inc | Longueuil | Aluminum |
| Aluminium DP | Longueuil | Aluminum Products |
| Aluminium Walker | Longueuil | Tout Entreprises et services, Balconies |
| Alégoria Beauté-Santé-Détente | Longueuil | Beauty & Fitness, Hairdressers & Beauty Salons |
| Am Beauty | Longueuil | Beauty & Health Spas |
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| Ameublement Abr | Longueuil | Furniture Stores |
| Amiante Proconsult Inc | Longueuil | Asbestos Removal & Abatement |
| Amicom Inc | Longueuil | Business Centres |
| Aménagement Gopelouse | Longueuil | Landscaping |
| Aménagement GoPelouse | Longueuil | Landscaping |
| Aménagement Paysager Artifex Inc | Longueuil | Landscaping |
| Ancrage Féminin | Longueuil | Massage Therapy |
| Andre Couture | Longueuil | Couture, COUTURE |
| Andre Poulin | Longueuil | Building Contractors |
| André Cycle & Sport Inc | Longueuil | Tout Commerces au détail |
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| André Cycle Sport Inc | Longueuil | Bicycle Stores |
| Andrée Lacourse Massothérapie-Approche Ostéopathique | Longueuil | Massage Therapy |
| Angelika Voyance | Longueuil | Astrologers & Psychics |
| Angélique-Voyance | Longueuil | Astrologers & Psychics |
| Animation Gonflable | Longueuil | Computer Graphics Design & Animation |
| Anna Lai Pu | Longueuil | pu |
| Annie Sleeth Hypnose Plus | Longueuil | Tout Entreprises et services |
| Appartements Terrasse De Sérigny | Longueuil | Apartment Rental |
| Appliance Parts Club | Longueuil | Appliance Parts & Supplies |
| Arboquébec | Longueuil | Tout Entreprises et services |
