Test-Retest Reliability, one of the fundamentals of science and technology is being able to reproduce with accuracy the same result. Otherwise, we don’t know how it works, why it works, how to use it or when it won’t work. In medicine, these ideas are a little more complicated given the inherent complexity of organisms and natural variations among them. Many tests are used to determine the status of a client but if another therapist takes over, questions arise if they would have scored the same way from the beginning and would be in the same stage of rehab. A recent analysis of a group of patients undergoing haemodialysis compared two physiotherapists doing the same tests 1 week apart. There should be no significant change in scores. In 88% of cases, across 6 tests with 39 patients, the physiotherapists scored the same way. This shows that the standardized education physiotherapists receive does have benefits. Knowing that you and your colleagues will score someone at the same level of function 9 out of 10 times gives you and by extension the client through confidence in the tools you have.