We investigated the impact of early brief chemotherapy on the natural history of primary testicular lymphoma. We compared the outcome for patients seen before 1980--a group primarily managed with orchiectomy and regional radiation--with those seen from 1980 to 1986--a prospectively and consecutively gathered group who were offered brief chemotherapy in addition to standard orchiectomy and irradiation. The historical and study groups were similar in clinical characteristics. However, the chemotherapy group had a better relapse-free survival, 93% v 50% (P less than .02), and overall survival, 93% v 50% (P less than .02). With a median follow-up of 44 months in the chemotherapy group, it is clear that the use of early, brief chemotherapy strongly alters the natural history of testicular lymphoma by preventing relapses, the large majority of which occur early after regional therapy. We conclude that a program incorporating orchiectomy, early brief chemotherapy, and involved-field radiation therapy confers the following benefits on patients with primary testicular lymphoma: (1) laparotomy is not needed for staging; (2) relapses, including those in the opposite testicle and CNS, are largely prevented; and (3) toxicity can be kept to a modest level acceptable in elderly patients.