A case-control study of 271 men with testicular cancer and 259 controls was conducted in the Washington, DC area to evaluate whether suggested risk factors could be responsible for the epidemic increases in testicular cancer in young men. No substantial risks were associated with a history of groin hernia operation, the common childhood diseases, allergies, x rays below the waist, venereal disease, vasectomy, or external means of elevating the temperature of the testis. Excess risks were associated with a history of undescended testis (RR = 3.7, CI = 1.5-9.5), testicular trauma (RR = 2.6, CI = 1.6-4.2), and mumps orchitis (RR = 5.8, CI = 0.7-129.7). It is unlikely, however, that any of these conditions has increased sufficiently over time to markedly affect the testicular cancer incidence patterns. Therefore, while the risk factors identified in this paper are of epidemiological interest, they do not account for the increase in testicular cancer in young men.