Recent studies on the strength of glass fibers suggest that the time is ripe for new, fundamental studies in this area which may significantly advance our understanding of the intrinsic strength of glasses. In order to set the stage, in this paper we define various terms (intrinsic and extrinsic strength and inert and environmental fatigue) and analyze techniques for their measurement. We illustrate and evaluate these parameters by means of literature data on silica and E-glass. In addition we present some preliminary new data on E-glass fibers using 2-point bending. These new data report higher strength than previously reported and some possible reasons for this are given. While these comments deal primarily with the science of strength, a better understanding of these issues may lead to improvements in glass technology and glass products.