| Ionization Spectroscopy for Chemical Analysis | Academic & Science |
| Isabela State College of Agriculture | Academic & Science |
| International Symposium on Computer Architecture | Academic & Science |
| International Society for Computers and Their Applications | Academic & Science |
| International Society of Christian Apologetics | Academic & Science |
| International Society of Caricature Artists | Academic & Science |
| International Society for Conversation Analysis | Academic & Science |
| International Student Christian Association | Academic & Science |
| Iowa Student Computer Association | Academic & Science |
| Institutio Superior De Ciencas Agropecuaria | Academic & Science |
| Iranian Student Cultural Association | Academic & Science |
| International Speedway Corporation Class A | Business |
| Indiana State Chiropractic Association | Community |
| Idaho School Counselors Association | Community |
| International Seascape18 class association | Community |
| Idaho School Counselor Association | Community |
| Illinois Soil Classifiers Association | Community |
| International School Counselor Association | Community |
| Iranian Students Cultural Association | Community |
| Indiana Sporting Clays Association | Community |
| Iowa School Counselor Association | Community |
| Irish Setter Club of America | Community |
| Inline Skating Club of America | Community |
| Independent Schools Cultural Alliance | Community |
| Indiana School Counselor Association | Community |
| Illinois School Counselor Association | Community |
| International Systemic Constellations Association | Community |
| International Shrine Clown Association | Community |
| International Safety Coach Association | Community |
| International Sport and Culture Association | Community |
| International Speech Communication Association | Community |
| International Scouting Collectors Association | Community |
| Interrupt Status Control A | Computing |
| Intelligent Synchronous Communications Adapter | Computing |
| International Show Car Association | General |
| Indiana Sprint Car Association | General |
| Idle Speed Control Actuator | General |
| International Show Caves Association | General |
| Information Strategic Cloze Assessment | General |
| I save children anywhere | General |
| International Swim Coaches Association | International |
| International Standards for Cytogenomic Arrays | International |
| International Society for Copier Artists | International |
| Integrated Support Command Alameda | Military and Defence |
| Indoor Soccer Coaches Association | Sports |
| International Sports Conditioning Association | Sports |
| Indiana Soccer Coaches Association | Sports |