2026 data ClinicalTrials.gov official source

Conditions: O

Compiled by PlainTrial Editorial, Clinical Trial Intelligence Editorial Team · January 1, 2026

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

829 conditions starting with "O"

Showing 351–400 of 829

Condition	Trials	Recruiting
Optic Neuropathy	3	3
Optic Pathway Glioma	1	1
Optic Pathway Gliomas	1	1
Optic, Atrophy, Hereditary, Leber	1	-
Optical Coherence Tomography	1	1
Optical Coherence Tomography (OCT) of the Retina	1	-
Optimism	1	-
Or Relapsed or Refractory Secondary Central Nervous System Lymphoma (SCNSL)	1	-
Oral and Throat Cancer	1	1
Oral Bacterial Infection	2	2
Oral Cancer	18	9
Oral Cancer , Oral Squamous Cell Carcinoma, Oral Cavity Cancer	1	1
Oral Candidiasis	1	-
Oral Carcinoma in Situ	1	1
Oral Cavity and Lip Precancerous Condition	1	-
Oral Cavity Cancer	13	5
Oral Cavity Carcinoma	5	3
Oral Cavity Dysplasia	1	1
Oral Cavity Infection	1	1
Oral Cavity Leukoplakia	1	-
Oral Cavity Mucosal Melanoma	1	1
Oral Cavity Neoplasm	1	1
Oral Cavity Squamous Cell Carcinoma	9	7
Oral Cavity Verrucous Carcinoma	1	-
Oral Chronic Graft-versus-host Disease	1	-
Oral Complications	2	-
Oral Complications of Chemotherapy	2	-
Oral Complications of Chemotherapy and Head/Neck Radiation	1	-
Oral Complications of Radiation Therapy	1	-
Oral Contraceptive	1	-
Oral Contraceptive Pill Adherence	1	-
Oral Contraceptive Use	1	-
Oral Disorder	1	-
Oral Drug Administration	1	1
Oral Dysplasia	2	2
Oral Feeding Outcomes	1	1
Oral Glucose Tolerance	2	2
Oral Health	5	2
Oral Herpes Simplex	1	-
Oral History	1	1
Oral Hormonal Contraceptive Use	1	1
Oral Hygiene	1	-
Oral Hygiene Education Methods	1	-
Oral Hygiene Reinforcement During Fixed Orthodontic Treatment	1	-
Oral Infection	1	1
Oral Infections	1	1
Oral Inflammation	1	1
Oral Intubation	1	-
Oral Lesions	1	1
Oral Leukoplakia	5	2

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