The clinical evaluation section of the Core Assessment Program for Intracerebral Transplantations (CAPIT) for Parkinson's disease (PD) was developed to standardize the clinical evaluation in cell transplantation trials, but also has been used in other therapeutic trials for PD. An important part of the CAPIT protocol is the standardized timed tests of motor function. In a recent revision of CAPIT, the Core Assessment Program for Surgical Interventional Therapies in Parkinson's Disease (CAPSIT-PD), the timed tests have been modified. There are some practical considerations that need attention when timed tests are used. They should be performed under the same circumstances with the patient in a defined condition and according to the same instructions from one time to another. Also, the examiner should not assist the patient, either directly or indirectly, by cueing. In addition to quantification of motor function as an outcome measure in therapeutic trials and other clinical research, timed tests also can be used for determining dopaminergic responsiveness in differential diagnosis of parkinsonism. Our experience is that timed tests are valuable quantitative and objective measures in scientific as well as clinical assessments of PD. Practical guidelines for and examples of these areas of use are provided.