Four media, Eagle's minimal essential medium with 10% fetal bovine serum (MEM/FBS), tryptic soy broth (TSB), 2-SP, and 4-SP, were compared for their ability to maintain the viability of Chlamydia trachomatis at 4 degrees C, -20 degrees C, -70 degrees C, and -176 degrees C (liquid nitrogen) over a 1-week period. 2-SP maintained viability of C. trachomatis to the greatest extent for all of the time intervals and temperatures examined. Therefore, in an attempt to further stabilize the viability of C. trachomatis, 2-SP was supplemented with various concentrations of bovine serum albumin (BSA) or fetal bovine serum (FBS). For the times and temperatures examined, 2-SP supplemented with 20% or 40% FBS or 5% BSA preserved infectivity to a greater extent than unsupplemented 2-SP. In some supplemented media, up to 65% of the infectivity was preserved after one week of storage at -176 degrees C, whereas only 0-3% of infectivity remained when stored in unsupplemented media at -20 degrees C and 4 degrees C, respectively. Therefore, supplementation of 2-SP with FBS or BSA can prolong the survival of chlamydia, which is critical in the transportation and storage of clinical specimens. In addition, storage for prolonged periods of time should be at -70 degrees C or lower temperatures.