Instrument Landing System 
Integrated Logistics Support 
Integrated Logistic Support 
International Launch Services 
Instrument Landing Systems 
Integrated Logistics System 
International Language Support 
Internet Locator Service 
Integrated Learning System 
Integrated Library System 
Intelligent Library System 
Identification Lists 
Information and Library Services 
Initial Launch Services 
Input-buffer Limiting Scheme 
Interactive Link Suite 
Intergovernmental Liason Staff 
International labour standards 
International Latitude Service 
International Launch Service 
International Lunar Society 
intracavity laser spectroscopy 
Ionization Loss Spectroscopy 
IBM Learning Services 
Ideal Liquidus Structures 
Imaginary Lat Syndrome 
Imaging Line Scanner 
Immediate Line Supervisor 
immunoliposomes 
immunolymphoscintigraphy