A new method for mounting protein crystals and other environmentally sensitive samples for room-temperature diffraction measurements is described. A crystal is retrieved using a microfabricated sample mount as recently reported, and the mount is inserted into a modified goniometer-compatible base. A transparent thin-wall polyester tube sealed at one end and filled with stabilizing liquid is then drawn over the crystal and sealed to the goniometer base. Compared with mounting using glass capillaries, this method can provide lower-background X-ray scattering, especially at higher resolutions; dramatically improved ease of crystal mounting with minimal chance of damage; accurate and reproducible crystal positioning relative to the goniometer base; improved crystal visibility and ease of alignment, especially for very small crystals; and compatibility with high-throughput approaches. Crystals can be rapidly screened and eliminated earlier in the data collection pipeline, and the cause of poor low-temperature diffraction can be diagnosed. © 2005 International Union of Crystallography Printed in Great Britain - all rights reserved.