NCI and the U.S. CDC are collaborating with the Cancer Registry of Norway to investigate risks of several cancers by examining serum levels of persistent organohalide chemicals, including DDT and PCB, as well as changes in the serum levels of those chemicals over time. Investigators found that p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), the primary DDT metabolite, was not associated with NHL overall but was associated with increased risk in certain subgroup analyses. Recent analyses have examined serum conCentreations of organochlorine compounds and risk of testicular germ cell tumors.