Cockroaches are known to contain powerful allergens; many asthmatics are allergic to cockroaches and in some areas cockroach sensitization is a very important indoor allergen, second only to that of house dust mites. A number of studies in the USA, which will be discussed in the section dealing with that country, have shown that cockroaches are an important risk factor for allergic asthma. However, in Europe, the prevalence of cockroach allergy in atopic or asthmatic populations seems to be much lower than in North America, ranging between 4.2% in Germany (Hirsch et al., 2000) and 27.8% in France (Dubus et al., 2001). Another study in Marseille ‘determined that the presence of Blatella germanica hypersensitivity among patients with asthma was 35% and was the most sensitive allergy after mite, grass pollens and cat allergens’ (Birnbaum et al., 1995). Studies in Croatia suggested that there is no relevant exposure to cockroach allergen in house dust samples from inland areas of Croatia (Macan et al., 2003). Observations in Switzerland suggested that allergy to cockroaches is uncommon in the country but can sometimes be detected (Mosimann et al., 1992). On the other hand, among Polish children, cockroach allergen is a very important factor of sensitivity after dust mites; concentrations of cockroach antigens in homes studied were higher than previously reported in other European countries. Children with hypersensitivity to cockroach allergens have severe asthma more often than children with other allergies (Stelmach et al., 2002).