Infectious elementary bodies of Chlamydia psittaci in tissue samples from field cases of enzootic abortion were placed in five different transport media (A to E). In one medium, in the absence of refrigerative storage, the organism remained viable for 30 days and at 4 degrees C for 34 days. This was medium D; it consisted of sucrose (74.6 g/litre), K2HPO4 (1.237 g/litre), L-glutamic acid (0.721 g/litre), fetal calf serum (10 per cent v/v), vancomycin and streptomycin (100 micrograms/ml) and nystatin and gentamicin (50 micrograms/ml). Samples of this transport medium were supplied to veterinary investigation centres throughout the UK. Of 1862 samples submitted for diagnosis of enzootic abortion only 1.55 per cent were so contaminated that chlamydiae could not be detected. This transport medium permits the isolation of C psittaci from clinical material for up to about one month, even in the absence of conventional storage facilities.