| identifier | No | Identifier[] | Business Identifier for study |
| title | No | string | Name for this study |
| protocol | No | Reference<PlanDefinition>[] | Steps followed in executing study |
| partOf | No | Reference<ResearchStudy>[] | Part of larger study |
| status | Yes | code | active / administratively-completed / approved / closed-to-accrual / closed-to-accrual-and-intervention / completed / disapproved / in-review / temporarily-closed-to-accrual / temporarily-closed-to-accrual-and-intervention / withdrawn |
| primaryPurposeType | No | CodeableConcept | treatment / prevention / diagnostic / supportive-care / screening / health-services-research / basic-science / device-feasibility |
| phase | No | CodeableConcept | n-a / early-phase-1 / phase-1 / phase-1-phase-2 / phase-2 / phase-2-phase-3 / phase-3 / phase-4 |
| category | No | CodeableConcept[] | Classifications for the study |
| focus | No | CodeableConcept[] | Drugs, devices, etc. under study |
| condition | No | CodeableConcept[] | Condition being studied |
| contact | No | ContactDetail[] | Contact details for the study |
| relatedArtifact | No | RelatedArtifact[] | References and dependencies |
| keyword | No | CodeableConcept[] | Used to search for the study |
| location | No | CodeableConcept[] | Geographic region(s) for study |
| description | No | markdown | What this is study doing |
| enrollment | No | Reference<Group>[] | Inclusion & exclusion criteria |
| period | No | Period | When the study began and ended |
| sponsor | No | Reference<Organization> | Organization that initiates and is legally responsible for the study |
| principalInvestigator | No | Reference<Practitioner / PractitionerRole> | Researcher who oversees multiple aspects of the study |
| site | No | Reference<Location>[] | Facility where study activities are conducted |
| reasonStopped | No | CodeableConcept | accrual-goal-met / closed-due-to-toxicity / closed-due-to-lack-of-study-progress / temporarily-closed-per-study-design |
| note | No | Annotation[] | Comments made about the study |
| arm | No | ResearchStudyArm | Defined path through the study for a subject |
| - id | No | string | Unique id for inter-element referencing |
| - extension | No | Extension[] | Additional content defined by implementations |
| - modifierExtension | No | Extension[] | Extensions that cannot be ignored even if unrecognized |
| - name | Yes | string | Label for study arm |
| - type | No | CodeableConcept | Categorization of study arm |
| - description | No | string | Short explanation of study path |
| objective | No | ResearchStudyObjective | A goal for the study |
| - id | No | string | Unique id for inter-element referencing |
| - extension | No | Extension[] | Additional content defined by implementations |
| - modifierExtension | No | Extension[] | Extensions that cannot be ignored even if unrecognized |
| - name | No | string | Label for the objective |
| - type | No | CodeableConcept | primary / secondary / exploratory |
