We investigated the pattern of glutathione S-transferase (GST) activity in the course of the development of Apis mellifera macedonica. GST activity is present in all developmental stages of A. mellifera macedonica. The highest activity towards the substrate 1-chloro-2,4-dinitrobenzene (CDNB) is found in the adult stage and the lowest in the egg. The kinetic characteristics of the whole enzyme change as the insect develops. Significant changes are observed in substrate specificity, inhibitor sensitivity and V(max). The number of isoenzymes and their rate of expression vary as the insect develops. However, two main isoenzymes are present in all developmental stages, one in the alkaline area and the other in the acidic. While in the larval stage the acidic isoenzyme is expressed at a slightly higher rate (52.2% over 47.8% for the alkaline isoenzyme), in the adult stage, the rate is reversed dramatically (13.24% and 84.2%, respectively).