| Alternative Systems Consulting | New Hampshire |
| Alternative Telecom, Inc. | North Dakota |
| AlternativeWireless.com | Texas |
| Alternergy Power System, Inc. | Texas |
| Alteron Therapeutics | |
| Alteryx, Inc. | California |
| Altesa Biosciences, Inc. | Georgia |
| Altest Corporation | California |
| Altex Computers & Electronics | Texas |
| AltexSoft | California |
| Altezza | Texas |
| AltezzaSys | California |
| Althera Code | |
| Altherr Web Design | Ohio |
| Altia, Inc. | Colorado |
| AltiBio, Inc. | California |
| Altice USA | New York |
| Altimeter Capital Management, L.P. | |
| Altimmune | Maryland |
| AltIndex | |
| Altineer | |
| Altinex, Inc. | California |
| Altiostar | Massachusetts |
| Altir | |
| Altira Group, LLC | Colorado |
| Altis Biosystems | North Carolina |
| ALTIS Computer Services, Inc. | Louisiana |
| Altispeed | North Dakota |
| Altitude 800 Corporation | California |
| Altitude Health, Inc. | |
| Altitude Marketing | |
| Altius Broadband, Inc. | Kentucky |
| Altivia Solutions, LLC | Colorado |
| Altivix | |
| Altizon, Inc. | New Jersey |
| Altman Solon | Massachusetts |
| Alto | Texas |
| Alto Neuroscience | California |
| Alto Palo | |
| Altogen Biosystems | Nevada |
| Altogen Laboratories | |
| Altoida | District of Columbia |
| Altolab | |
| Altomec Endoscopy, Inc. | Michigan |
| Altor Systems | California |
| Altoros | California |
| Altos | New Hampshire |
| Altos Labs | |
| Altos Ventures Management, Inc. | |
| Altova | Massachusetts |