| Acronym | Meaning |
| ISD | Ion Stimulated Desorption |
| ISDN | Integrated Services Digital Network |
| ISDN | Isosorbide Dinitrate |
| ISE | Ion Selective Electrode |
| ISE | Iterative Secular Equation (method For Solving The Schroedinger Equation) |
| ISEA | International Society For Exposure Analysis |
| ISEC | Inverse Size-exclusion Chromatography |
| ISEC | Inverse Steric Exclusion Chromatography |
| ISEE | International Society For Environmental Epidemiology |
| ISEELS | Inner-shell Electron Energy Loss Spectroscopy |
| ISES | International Solar Energy Society |
| ISF | Interstitial Fluid |
| ISFET | Ion-Sensitive Field-Effect Transistor |
| ISFSI | Independent Spent Fuel Storage Installation |
| ISG | International Stratigraphic Guide |
| ISGF | Interferon-stimulated Gene Factor |
| ISGO | International Structural Genomics Organization |
| ISH | In Situ Hybridization |
| ISHM | International Society For Hybrid Microelectronics |
| ISHOW | Information System For Hazardous Organics In Water |
| ISI | Information Systems Inventory |
| ISI | Institute For Scientific Information |
| ISIRS | International Sorption Information Retrieval System |
| ISIS | Industrial Site Information System |
| ISIS | Image-selected In Vivo Spectroscopy |
| ISLAR | International Symposium On Laboratory Automation And Robotics |
| ISLOCA | Inter-system Loss-of-coolant Accident |
| ISLSCP | International Satellite Land Surface Climatology Project |
| ISM | Interaction Site Model (in Statistical Mechanics Of Fluids) |
| ISM | Intersecting Spheres Model (for Electronic-structure Calcns.) |
| ISM | Interstellar Medium |
| ISM | Inverse Scattering Method |
| ISMAR | International Society Of Magnetic Resonance |
| ISME | Ion-selective Microelectrode |
| ISO | IR Space Observatory |
| ISO | International Organization For Standardization |
| ISOF | Insoluble Org. Fraction (e.g. |
| ISOLDE | Isotope Separator On Line |
| ISP | In-line Strip Production |
| ISPAC | International Society For Polycyclic Aromatic Compounds |
| ISPCR | In Situ Polymerase Chain Reaction |
| ISPD | Ion-selective Photodiode |
| ISPGAA | In Situ Prompt Gamma-ray Activation Analysis |
| ISPM | In-situ Particle Monitor |
| ISRA | Image-space Reconstruction Algorithm |
| ISRE | Interferon-stimulated Response Element |
| ISRI | Institute Od Scrap Recycling Industries |
| ISRM | International Society For Rock Mechanics |
| ISRS | Impulsive Stimulated Raman Scattering |
| ISS | Intermediate Solid Solution |