| PROS | Paediatric Radiation Oncology Society 
| Others |
| PROS | Parks Recreation and Open Space
| Others |
| PROS | Parts and Repair Ordering System
| Others |
| PROS | Pathogen Related Oral Spirochetes
| Others |
| PROS | Patient Reported Outcomes Survey
| Others |
| PROS | Patient Reported Outcomes Surveys
| Others |
| PROs | Patient-reported outcomes
| Others |
| PROS | Pediatric Research in Office Settings
| Others |
| PROS | Peer Referral and Orientation Staff
| Others |
| PROS | Personalized Recovery Oriented Services
| Others |
| PROS | Personalized Recovery Oriented Systems
| Others |
| PROS | Personalized Recovery-Oriented Services
| Others |
| PROS | Philadelphia Regional Ophthalmic Society
| Others |
| PROS | Physical Rehabilitation Outpatient Services
| Others |
| PROS | PIK3CA Related Overgrowth Spectrum
| Others |
| PROS | Police Reaching Out to Students
| Others |
| PROS | Police Reporting And Occurrence System
| Others |
| PROS | Positive Reaction Obstructive Safety
| Others |
| PROS | Positive Reflection Of Success
| Others |
| PROS | Professional Reliable Oilfield Service
| Others |
| PROS | Professional Retail Outstanding Salesperson
| Others |
| PROS | Propulsion Subsystem
| Others |
| PROS | Pseudo Ros
| Others |
| PROS | Pug Rescue Of Sacramento
| Others |