The standard measurements of the properties of orthodontic wire are of limited value to the orthodontist, and clinical impressions of wire behavior are unreliable. This article discusses the properties of clinical relevance to the selection of wires for the initial alignment of irregular teeth. These concepts are illustrated by measurements made on some commonly used orthodontic wires. It is evident that a compromise often has to be made between flexural rigidity and elastic recovery and that no single figure or merit can adequately characterize a wire in both respects. It is necessary for the clinician to understand the properties of importance and the nature of the compromise in order to be able to select the most appropriate wire for a particular application. An investigation into the load-deflection characteristics of a single span reveals that many arches are remarkably stiff and are not capable of applying light forces. The effects of incorporating loops in the wire in order to modify span characteristics are discussed with reference to the contributions of the different components.