Researchers spend many years developing new treatments or medicines in the laboratory before involving people. They then plan the clinical trial to progress in a series of steps called phases. Every phase considers whether the risks outweigh the benefits.
Information gathered in each phase determines whether the study can move on to the next phase, and whether the drug or treatment is approved for use.
There can be up to four phases, but not all clinical trials go through every phase. See below for a description of different phases.
Watch this video to find out more about the different phases.
How clinical trial phases work
Phase 1 – Safety
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Phase 2 – Effectiveness
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Phase 3 – Comparison
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Phase 4 – Follow-up
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→ READ MORE: Randomised controlled trials
Video: The 4 phases of clinical trials
In this video, Dr Elizabeth Hovey explains the four different phases of a clinical trial.
Key resource
Download a PDF booklet on this topic.
More resources
All updated content has been clinically reviewed by A/Prof Brett Hughes, Senior Staff Specialist, Medical Oncology, Royal Brisbane and Women’s Hospital and The Prince Charles Hospital, and Associate Professor, The University of Queensland, QLD. This edition is based on the previous edition which was reviewed by the following panel: A/Prof Brett Hughes (see above); Christie Allan, Clinical Trials Lead, Cancer Council Victoria, VIC; Dawn Bedwell, 13 11 20 Consultant, Cancer Council Queensland, QLD; Joanne Benhamu, Senior Research Nurse, Team Lead, Lung, Colorectal and Palliative Care Trials, Parkville Cancer Clinical Trials Unit, Peter MacCallum Cancer Centre, VIC; Louise Dillon, Consumer; Sabina Jelinek, Clinical Nurse Research, St John of God Murdoch Hospital, WA; Chloe Jennett, Program Coodinator, Cancer Research, Cancer Council NSW; Carmel McCarthy, Consumer; Alison Richards, Research Unit Manager, Medical Oncology Clinical Trials Unit, Flinders Medical Centre, SA; Prof Jane Ussher, Translational Health Research Institute (THRI), School of Medicine, Western Sydney University, NSW; Prof Janette Vardy, Medical Oncologist, Concord Cancer Centre, and Professor of Cancer Medicine, The University of Sydney, NSW.
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