| Islamic Society of Arlington Texas | Academic & Science |
| Intelligent Students At Twin Groves | Academic & Science |
| Initial Surface Absorption Test | Academic & Science |
| Illinois Student Achievement Test | Academic & Science |
| International Security Advisory Team | Business |
| Inmarsat | Business |
| International Schools Association of Thailand | Community |
| Integrated Service Access Terminals | Computing |
| Interim Software Acceptance Test | Computing |
| Information Systems and Applied Technologies | Computing |
| Inflatable Sound Attenuation Technology | Computing |
| Intelligent Systems and Assistive Technologies | Computing |
| IIST Admission Test | Engineering Entrance Exam in India |
| Integrated Shipping & Assembly Tooling | General |
| Illinois State Assessment Test | General |
| Institut Superieur de l'Automobile et des Transports | General |
| Illinois Standard Achievement Test | General |
| Impervious Surface Analysis Tool | General |
| Interactive Self Assessment Tool | General |
| Illinois Standard Assessment Tests | General |
| Illlinios Standard Achievment Test | General |
| Idaho Standard Achievement Test | General |
| Illinois State Achievement Test | General |
| IBM Service Assistant Tool | General |
| Image Station Automatic Triangulation | General |
| Integrated Services Assessment Tool | General |
| Information Sharing Assessment Tool | General |
| Interactive Scenario Authoring Tool | General |
| Illinois Standards Assessment Test | General |
| Illinois Standards Achievement Test | General |
| Idaho Standards Achievement Tests | General |
| Itemsillinois Standards Achievement Test | General |
| Idaho Standards Achievement Test | General |
| Interactive Specification Acquisition Tools | General |
| In Situ Adaptive Tabulation | General |
| Institute of Salutary Academic Training | Governmental |
| International Subarachnoid Aneurysm Trial | International |
| International Seismic Application Technology | International |
| International Student Admissions Test | International |
| International Students Admissions Test | International |
| International Student Admission Test | International |
| Internet Security Awareness Training | Internet |
| Irish Sleep Apnoea Trust | Regional |
| Integrated Science and Technology | Technology |
| Inginternational Science and Technology | Technology |
| International Science and Technology | Technology |