Zr-Al alloys based on the intermetallic compound Zr3Al are presently being considered as structural materials for use in nuclear environments. Theoretically, the single-phase Zr3Al alloy should contain 8.97% Al, but in practice single phase material is not produced, and alloys containing approximately 8.0 to 8.5% Al contain a dispersion of α-Zr solid solution in the Zr3Al matrix (fig. 1). At higher Al concentrations Zr2Al may also be present.In this paper we describe the structures observed in a Zr-8.3% Al alloy containing up to 1300 μg/g hydrogen. Hydrogen was introduced into the alloy in two ways. The first technique involved the exposure of a weighed sample, at 650°C to a known volume of hydrogen at a predetermined pressure. The pressure was monitored during hydriding until it dropped to a value corresponding to the required uptake of hydrogen.