The rate at which silk, particularly weighted silk, will deteriorate on exposure to light, heat, and moist air cannot be predicted simply from the amount of weighting or other substances present on the silk. A laboratory test which will indicate the relative stability of silks is needed. The aging, as revealed by changes in breaking strength, of a variety of silk and weighted-silk cloths when stored in the dark, when exposed to the daylight received through a north window (natural aging), or to the radiation from the glass-enclosed carbon-arc lamp under controlled conditions of temperature and relative humidity of the atmosphere (accelerated aging) was studied. Data on the accelerated aging of some typical silk dress fabrics were obtained. An accelerated aging test is proposed.