Exposure and sensitization to cockroach allergens is an importantrisk factor for allergic disease in humans. Despite a recent burgeoningof clinical and socioeconomic studies regarding environmentalpervasiveness and human exposure to cockroach allergens, little isknown about the basic biology of these proteins. The purpose of thisstudy was to ascertain gene expression patterns and the tissuedistribution of Blattella germanica allergen 1 (Bla g1), a perennial indoor environmental allergen, thought to be involvedin digestion in cockroaches. We also investigated the relativepotential contribution of different life stages of the German cockroachto environmental Bla g 1. Enzyme-linked immunosorbent assay was used toquantify the Bla g 1 contents of feces and various anatomical tissues,and Northern blot analysis was used to elucidate tissue-specificexpression of Bla g 1. Results showed that the Bla g 1 protein is mostprevalent in the midgut, and the Bla g 1 gene is exclusively expressedby midgut cells. Although Bla g 1 is produced by both sexes and alllife stages of the German cockroach, adult females produce and excretesignificantly more Bla g 1 in their feces than males or nymphs, evenwhen corrected for body mass or mass of voided feces. Our results showthat the concentration of Bla g 1 in feces of adult females is 6- to 7-and 30-fold higher than in adult males and nymphs, respectively,probably because females process more food than other life stages ofthe German cockroach.