| Instruction Set Architecture C | Academic & Science |
| Immuno-Solid phase Allergy Chip | Academic & Science |
| International Society for Analytical Cytology | Academic & Science |
| Illinois Student Assistance Commission | Academic & Science |
| ISRO Satellite Centre | Academic & Science |
| Istituto di Scienze dell'Atmosfera e del Clima | Academic & Science |
| Invasive Species Advisory Committee | Business |
| Information Systems Advisory Committee | Business |
| Industry Sector Advisory Committee | Business |
| I C Isaacs & Company, Inc. | Business |
| Iowa State Association of Counties | Community |
| International Survivors Action Committee | Community |
| Institute for the Study of American Cultures | Community |
| Independent Schools Adventure Cruises | Community |
| Intelligent System Analytic Computer | Computing |
| Isa Client | Computing |
| Intelligent Secure Autonomic Controller | Computing |
| Intelligent System For Aircraft Conflict | General |
| In Situ Additive Construction | General |
| Information Sharing And Analysis Centers | General |
| Intelligent Soft Arm Control | General |
| Instructor Signature to Add a Class | General |
| Intelligence Sharing And Analysis Center | General |
| Information Sharing Analysis Center | General |
| Information Sharing Analysis Centre | General |
| International Standard Accuracy Contest | General |
| Iprobe Surveillance Automation Communication | General |
| International Society for Advancement of Cytometry | International |
| Instituto de Sociología Aplicada de la Comunicación | International |
| Internet Self Access Centre | Internet |
| internet Speech Audio Codec | Internet |
| Immuno-solid phase allergen chip | Medical |
| Immune Stimulating Antibody Conjugate | Medical |
| Immune System Activation Of Coagulation | Medical |
| International Schools Athletic Conference | Sports |
| Idol Star Athletic Competition | Sports |
| Idol Star Athletics Championships | Sports |
| Independent Sports Alliance of California | Sports |