The incidence of testicular cancer has increased considerably in this century. Current hypotheses (most specifically, those concerning environmental estrogens) show inconsistencies with this increase, either in terms of time course or individual exposure to proposed promoters. This new hypothesis, which attributes the increased incidence in testicular cancer to our current more iron-replete dietary status, is devoid of these inconsistencies. Evidence to support this hypothesis includes the following: (a) the iron-related mechanism of drugs used in the treatment of testicular cancer, (b) dietary associations with disease frequency, (c) the similarity of time course between historic increases in testicular cancer incidence and dietary iron availability, and (d) potential genetic associations with hemochromatosis. The link between incidence of the cancer and cyptorchidism is also addressed. The article concludes with potential experimental approaches to test the hypothesis.