[en] This symposium projected several important themes that should not be obscured by the wealth of information presented in these papers. Emission tomography is capable of answering critically important biomedical questions concerning neurotransmitter functions in living patients. As emission tomography is developed, each step must be perfected and validated until the data provided are unambiguous and reliable. The validated method should then be employed to test important physiological hypotheses not now capable of being answered by alternative methods. Ultimate transfer to patient management requires a further progression of accomplishments: we must test whether or not the new physiologic data can help clinicians make important decisions. Only then should we introduce into clinical practice those new studies that have proven to be both reliable and cost effective