As Drosophila melanogaster occupies an important position within the test battery for mutagens and carcinogens, it is of interest to study the xenobiotics metabolism of this insect. Likewise, the genetic control of these important enzyme systems falls within this interest. Our attempt was to get new strains, which show changes in their xenobiotics metabolism. This was done by a mutagenization and selection procedure for the second chromosome. The 44 fertile homozygous inbred strains produced by this selection were first tested for DDT resistance. Some of them showed LT50 values which were remarkably higher than that of the original strain Berlin K. Aflatoxin B1 metabolism in two of the new strains (H349 and H362), Berlin K, and Hikone-R was compared, whilst aldrin epoxidase activity was compared in strains H349, H362, Berlin K, vestigial, and Karsnäs-R. The metabolism studies were carried out in vitro with testes tissue of the different strains. The metabolism in testes is of specific interest because this tissue is most often used in mutagenicity testing. In the AFB1 assays of the up to 12 observed metabolites three could be identified as AFB2a, AFM1, and AFR0. Hikone-R produced mostly AFR0 (3.43% of the initial AFB1 concentration) and small amounts of AFM1 (0.59% AF and AFB2a (0.36% AF). The strain Berlin K showed only a low production of AFB2a (0.48% AF), while the strain H349 formed AFR0 (6.02% AF) and AFM1 (0.75% AF). The AFM1 appeared in even higher amounts than with Hikone-R. On the other hand, H362 showed the lowest activity in AFB1 metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)