Medical Organizations
- Optometric Extension Program Foundation (OEPF)
- Orange County Dental Society (OCDS)
- Orange County Medical Association (OCMA)
- Orange County Optometric Society (OCOS)
- Orbis International (Orbis)
- Oregon Association of Acupuncturists (OAA)
- Oregon Association of Naturopathic Physicians (OANP)
- Oregon Board of Licensed Professional Counselors and Therapists (OBLPCT)
- Oregon Board of Naturopathic Medicine (OBNM)
- Oregon Counseling Association (OCA)
- Oregon Hypnotherapy Association (OHA)
- Oregon Medical Association (OMA)
- Oregon Medical Board (OMB)
- Oregon Physical Therapy Association (OPTA)
- Oregon Psychological Association (OPA)
- Oregon Society of Clinical Hypnosis (OSCH)
- Organisation Europeenne pour le Controle de Qualite; European Organization for Quality Control (OECQ)
- Organisation Mondiale de Gastro-Enterologie; World Organization of Gastroenterology (OMGE)
- Organisation Mondiale de la Sante; World Health Organization (Switzerland) (OMS)
- Organization for Economic Cooperation and Development (OECD)
- Organization of Latino Social Workers (OLASW)
- Orthodontic Technicians Association; Orthopaedic Trauma Association (OTA)
- Orthopedic Research and Education Foundation (OREF)
- Osteopathic Cranial Academy (OCA)
- Österreichische Akademie der Wissenschaften; Austrian Academy of Sciences (OAW)
- Pacific Association of Pediatric Surgeons (PAPS)
- Pacific Northwest Vascular Society (PNWVS)
- Palm Beach County Medical Society (PBCMS)
- Palmetto State Chiropractic Association (PSCA)
- Pan-American Health Organization (PAHO)
- Pan-American Medical Association (PAMA)
- Pan-American Pharmaceutical and Biochemical Federation (PPBF)
- Pan-Pacific Surgical Association (PPSA)
- PAs in Virtual Medicine and Telemedicine (PAVMT)
- Pathological Society of Great Britain and Ireland (PSGBI)
- Patient-Centered Outcomes Research Institute (PCORI)
- Pediatric Infectious Diseases Society (PIDS)
- Pediatric Nurse Practitioner Association (NAPNAP)
- Pediatric Nursing Certification Board (PNCB)
- Pediatric Stress and Anxiety Disorders Clinic (PSADC)
- Pedorthic Footcare Association (PFA)
- Pennsylvania Academy of Pediatric Dentistry (PAPD)
- Pennsylvania Chiropractic Association (PCA)
- Pennsylvania Coalition of Nurse Practitioners (PCNP)
- Pennsylvania Counseling Association (PCA)
- Pennsylvania Dental Association (PDA)
- Pennsylvania Medical Society (PAMED)
- Pennsylvania Optometric Association (POA)
- Pennsylvania Podiatric Medical Association (PPMA)
- Pennsylvania Psychological Association (PPA)
- Pennsylvania Society for Clinical Social Work (PSCSW)
- Pennsylvania Speech-Language-Hearing Association (PSHA)
- Pennsylvania State Nurses Association (PSNA)
- Peruvian American Medical Society; Pennsylvania Association of Medical Suppliers (PAMS)
- Pharmaceutical Research and Manufacturers of America (PhRMA)
- Pharmaceutical Society of Great Britain (PSGB)
- Pharmaceutical Society of Ireland; Pharmaceutical Society of Ireland (PSI)
- Pharmaceutical Society of Northern Ireland (PSNI)
- Phi Alpha Honor Society (PAHS)
- Phoenix Obstetrical & Gynecological Society (POGS)
- Phoenix Urological Society (PUS)
- Physician Assistants Orthopaedic Surgery (PAOS)
- Physician Office Managers Association of America (POMAA)
- Physicians' Association for Anthroposophic Medicine (PAAM)
- Physicians Committee for Responsible Medicine (PCRM)
- Physicians for Humanity (PFH)
- Physicians for Human Rights (PHR)
- Physicians for Life (PFL)
- Pi Delta National Honor Society (PDNHS)
- Pima Dental Study Club (PDSC)
- Plastic Surgery Research Council (PSRC)
- Point-of-Care Ultrasound Certification Academy (POCUS)
- Polish-American Medical Society (PPMS)
- Postpartum Support International (PSI)
- Price-Pottenger Nutrition Foundation (PPNF)
- Problem Gambling Network of Ohio (PGNO)
- Professional Association of Therapeutic Horsemanship International (PATH Intl)
- Professional Eyecare Resource Co-Operative (PERC)
- Psi Chi, The International Honor Society in Psychology (PSI CHI)
- Psychiatric Association of Naturopathic Physicians (PsychANP)
- Psychological Society of America (PSA)
- Psychology Interjurisdictional Compact (PSYPACT)
- Public Health Institute (PHI)
- Queen's Institute of District Nursing (QJDN)
- Radiological Society of North America (RSNA)
- Recreational Therapist, Registered (RTR)
- Red Cross Society (UK) (RCS)
- Redwood Psychological Association (RPA)
- Regional Hospitals Consultants' and Specialists' Association (RHCSA)
- Registry of Interpreters for the Deaf, Inc. (RID)
- Rehabilitation Engineering and Assistive Technology Society of North America (REATSNA)
- Renal Physicians Association (RPA)
- Research Institute of Molecular Pathology (RIMP)
- Rhinoplasty Society (RS)
- Rhode Island Medical Society (RIMS)
- Richmond Academy of Medicine (RAM)
- Riley County Medical Society (RCMS)
- Riverside County Medical Association (RCMA)
- Robert T. Freeman Dental Society (RTFDS)
- Royal Air Force Medical Services (RAFMS)