The disaccharide trehalose is found to be effective for stabilization of active recombinant retroviruses in an amorphous dry state achieved through ambient-temperature vacuum dehydration of retroviral supernatants. Studies revealed that trehalose is a significantly better desiccation protectant than sucrose, glucose, and dextran : dextran has essentially no protective effect on retroviral survival after drying and rehydration. X-ray diffractometry of the retroviral supernatant dried with trehalose demonstrated its amorphous nature. The ability to dehydrate retroviral stocks at ambient temperatures into a stable glassy state will have a profound effect for researchers and commercial biotechnology companies which supply retroviral vectors for human gene therapy and basic research.