PTI
- Internet Assigned Numbers Authority
- PT1 (disambiguation)
- Page-table isolation
- Pakistan Tehreek-e-Insaf
- Palomar Testbed Interferometer
- Pardon the Interruption
- Parent-teacher interview
- Partai Tionghoa Indonesia
- Pennsylvania Transportation Institute
- Philippine Tobacco Institute
- Physical training instructor
- Piedmont Triad International Airport
- Pittsburgh Technical Institute
- Portugal Telecom
- Powertech Technology
- Premier Travel Inn
- Press Trust of India
- Pretrial Intervention Program
- Produce Traceability Initiative
- Proof Tracking Index
- Ti plasmid
- Vehicle inspection
- WTII Records