The influence of temperature and relative air humidity on the stability of ceftriaxone disodium (CTN) in Biotrakson and Tartriakson was investigated. At RH = 0%, the degradation of ceftriaxone was the first-order reaction, while at RH from 50.9% to 76.4% it was an autocatalytic first-order reaction relative to the substrate concentration. The influence of temperature on the stability of CTN was described by the following equations in the case of Biotrakson: RH =0% ln k = (-23488 +/- 7320) x 1/T+ 45.1; RH = 76.4% ln k = (-9492 +/- 1128) x 1/F + 16.1, and for Tartriakson: RH = 0% ln k = (-23491 +/- 7370) x 1/T + 42.4; RH = 76.4% ln k = (-10397 +/- 3034) x 1/T + 18.8. The influence of humidity on the stability of Biotrakson was described by the following equation: ln k = (0.0823 +/- 0.0272) x RH% -17.0 and for Tartriakson ln k = (0.0895 +/- 0.0246) x RH% -17.6.