| Cambridge International Studies Association | Academic & Science |
| Carolinas Integrated Sciences Assessments | Academic & Science |
| Certified Information Systems Auditor (us) | Accounts and Finance |
| Computer and Information Science Association | Business |
| Community Information Strategies Australia | Business |
| Corporate Investment Strategic Alliance | Business |
| China Iron and Steel Association | Business |
| China Iron & Steel Association | Business |
| Casting Industry Suppliers Association | Business |
| Cybersecurity and Infrastructure Security Agency | Business |
| Consumers for Internet Safety Awareness | Community |
| Catholic Information Service for Africa | Community |
| Crossroads In the Study of the Americas | Community |
| Carolinas Integrated Sciences and Assessments | Community |
| Community Involved In Sustaining Agriculture | Community |
| C4i Integration Support Activity | Computing |
| Cyber Intelligence Security Agency | Computing |
| Center for Information Security and Assurance | Computing |
| Certified Information Systems Auditor | Computing |
| Certified Information Sytems Auditor | General |
| Central Illinois Service Access | General |
| Centre for Intelligent Systems And | General |
| Cybersecurity Information Sharing Act | Governmental |
| Council of International Students Australia | Governmental |
| California International Sailing Association | International |
| Committee on International Scientific Affairs | International |
| College of International Security Affairs | International |
| Certified Information System Auditor | Jobs |
| Computational Intelligence and Signal Analysis | Maths |
| Clinical Immunization Safety Assessment | Medical |
| Canadian Institute for the Study of Antisemitism | Regional |
