This review summarizes studies comparing the epidemiology of asthma, allergic rhinitis, and atopic dermatitis in eastern versus western German populations. These studies clearly revealed that the prevalence of physician-diagnosed allergic rhinitis was higher in western Germany than in eastern Germany. The rate for asthma also tended to be higher in western than in eastern populations, whereas a tendency for less atopic dermatitis was found in western German children. When sensitization rates, as measured by RAST and skin-prick tests, were compared, a clear increase was found in western versus eastern young-adult German populations. This phenomenon may be related to exposure to different allergens, such as those associated with nutritional patterns or pet ownership, as well as to different environmental factors, such as outdoor and indoor pollutants. If lifestyle or environmental factors play a role in developing allergic sensitization, then one would expect the rates of sensitization in eastern and western Germany to converge as the two societies become more similar.