- Accountants
- Accounting Service
- Acoustic Consultants
- Acoustical Contractors
- Acupuncturists
- Adaptive Clothing
- Adjusters
- Adult Entertainment
- Adventure Games
- African Restaurants
- Agricultural Consultants
- Aids Services
- Air Cargo Service
- Air Conditioning
- Air Conditioning Contractors
- Air Purifiers
- Air Travel
- Aircraft Engines
- Aircraft Maintenance
- Airport Transportation Service
- Airports
- All-Terrain Vehicles
- Aluminum Products
- Ambulance Service
- Ambulances
- American Restaurants
- Amusement Machines
- Animal Breeders
- Animal Control
- Animal Medications
- Animal Shelters
- Antique Dealers
- Antiques
- Apartment Hotels
- Apartment Rental
- Apartments
- Appliance Repair
- Appraisers
- Aptitude Testing
- Architectural Technologists
- Arenas
- Art Supplies
- Artists
- Arts and Crafts Stores
- Arts and Crafts Supplies
- Asian Noodle Restaurants
- Asian Restaurants
- Asphalt Products
- Assembly Service
- Association Management
- Associations
- Auctions
- Audiovisual Consultants
- Audiovisual Equipment
- Audiovisual Production Service
- Auto Body Repair and Painting Shops
- Auto Body Shop Equipment
- Auto Glass
- Auto Repair Equipment
- Auto Repair Garages
- Auto Repair Self-Service Garages
- Automated Teller Manufacturers
- Automatic Fire Sprinkler Systems
- Automation Systems
- Automotive Springs
- Aviation Consultants
- Awnings