Background and Purpose: Medical diagnoses are not sufficient to guide physical therapy intervention. To provide a rational basis for treatment selection by physical therapists, we developed a set of diagnoses at the level of impairment that are relevant to the human movement system. The diagnoses describe the primary human movement system problem and provide a basis for matching a specific problem with appropriate treatment. The purposes of this 3-patient case report are to illustrate an updated version of the diagnostic system and to show how treatment decisions can be made relative to both the movement system diagnosis and the patient's prognosis. Case Descriptions and Outcomes: We diagnosed 3 patients with hemiplegia due to stroke as having 3 different movement system problems: force production deficit, fractionated movement deficit, and perceptual deficit. Specific intervention and actual patient outcomes for each case are outlined. Discussion: Use of movement system diagnoses may have multiple benefits for patient care. The possible benefits include decreasing the variability in management of patients with neuromuscular conditions, minimizing the trial-and-error approach to treatment selection, improving communication among health care professionals, and advancing research by enabling creation of homogenous patient groupings.