Kinetics of photochromic reactions was studied in azobenzene derivatives: azobenzene-containing crown ethers, and 4-methoxy-4'-halogen-substituted azobenzenes capable of forming liquid crystalline phases. The photoactive materials were dissolved in alkanes, and in polymer and liquid-crystalline matrices. The isomerisation reactions follow the first order kinetics, in some polymer matrices, however, a dispersion of the rate constants was found. Thermal cis-trans isomerisation rates of halogen-substituted azobenzenes in n-heptane were found practically independent of the substitutent. Kinetics of the same reactions in liquid crystalline matrices seems to exhibit anomalies near phase transitions of the matrices.