A model was developed assuming that the occurrence and the development of physiological disorders are effects of a balance between processes of disorder formation and scavenging of initiating compounds. Based on this (simplified) mechanism and applying the fundamental rules of chemical kinetics, the differential equations can be derived. The observed effects depend on initial levels of some nutrients (N), free radicals (Ra) and scavenging activity (SS). All three types of compounds do depend on the growing conditions prior to harvest, and hence on season, weather and climate. Postharvest development of disorders (PD) depends also on conditions during storage, e.g. temperature and CO2 level. Thus their influence was incorporated into a model based on fundamental knowledge in that sphere. The benefit of the developed model is that it allows simulating very different ranges in type of development of disorder. From very fast and reaching high level of occurrence, very fast but stabilised at low level of occurrence, to slow but reaching high level of occurrence, and slow and stabilised at low level of occurrence. And of course simulating of cases where the disorder occurrence is not observed at all. The model was checked against measured data on pears, indicating that the approach seems to be realistic and powerful enough to pursue. Existing data are however gathered in a manner not suitable for this approach. Therefore further studies on dynamics of physiological disorders require improvement of experimental methods.