A partial cDNA clone of the vitellogenin gene from the cockroach Blattella germanica has been isolated from a cDNA expression library using an anti-vitellin-vitellogenin antiserum probe. The analysis of cDNA inserts gave a sequence of 2,645 nucleotides corresponding to the 3' region. The deduced amino acid sequence is 825 residues long and is similar to the homologous portion of the vitellogenin of other insect species, especially that of the mosquito Aedes aegypti. RNA hybridization studies indicated that the vitellogenin gene expression is limited to the fat body of adult females. The pattern of expression during the first vitellogenic cycle was approximately parallel to that of vitellogenin production by the fat body previously described. The availability of a cDNA probe for the B. germanica vitellogenin gene represents a useful tool to study the molecular action of hormones affecting vitellogenin synthesis in this species.