2026 data ClinicalTrials.gov official source

Conditions: O

Compiled by PlainTrial · January 1, 2026

Every condition beginning with O that has a registered US clinical trial, with how many studies cover each.

820 conditions starting with "O"

Showing 151–200 of 820

Condition	Trials	Recruiting
Odor Intensity Ratings	1	1
Oesophageal Adenocarcinoma	1	-
Oesophageal Cancer	1	1
Oesophageal Squamous Cell Carcinoma	1	-
Oesophagitis, Eosinophilic	1	-
Off Label Use of Medications in Pediatric Patients	1	1
Off Pump Coronary Artery Bypass Surgery	1	1
Officers' Skills and Behaviors	1	-
oGHVD	1	1
oGVHD	1	1
OHT - Ocular Hypertension	2	1
OIC	1	-
Oily Skin	1	-
Old Age	2	1
Old Age; Debility	1	1
Older Adult	2	-
Older Adults	24	10
Older Adults (50-90 Years)	1	1
Older Adults (65 Years and Older)	5	4
Older Adults Without Any Specific Clinical Condition	1	1
Older Cancer Patients	1	-
Older People	2	1
Olfaction Disorders	1	-
Olfactory Disorder	4	2
Olfactory Dysfunction	1	1
Olfactory Impairment	1	1
Olfactory Neuroblastoma	1	1
Oligo-metastaic Urothelial Carcinoma	1	1
Oligoastrocytoma	3	1
Oligoastrocytoma, Mixed	2	-
Oligodendroglioma	15	7
Oligodendroglioma of Brain	1	1
Oligodendroglioma, Adult	2	-
Oligodendroglioma, Childhood	1	-
Oligodendroglioma, IDH-Mutant and 1p/19q-Codeleted	1	1
Oligodendrogliomas	1	-
Oligohydramnios	2	1
Oligomenorrhea	1	1
Oligometastasis	6	5
Oligometastatic	1	1
Oligometastatic Breast Carcinoma	1	1
Oligometastatic Disease	5	4
Oligometastatic Esophageal Adenocarcinoma	1	-
Oligometastatic Gastric Adenocarcinoma	1	-
Oligometastatic Intrahepatic Cholangiocarcinoma	1	1
Oligometastatic Malignant Solid Neoplasm	2	1
Oligometastatic Prostate Adenocarcinoma	1	1
Oligometastatic Prostate Cancer	1	1
Oligometastatic Prostate Cancer (OMPC)	2	2
Oligometastatic Prostate Carcinoma	7	5

Data sourced from official public datasets. See our methodology for details.