A patient with prolymphocytic leukemia (PLL), a lymphoproliferative disorder that carries a poor prognosis, is presented. The disease was diagnosed at an early stage and treatment could be delayed for four years. When massive, painful splenomegaly developed, splenic irradiation (SI) was chosen as the primary form of therapy and an excellent systemic response could be achieved. Our observation is in agreement with preliminary studies, which advocate SI as the primary form of therapy in PLL. Furthermore, it is emphasized that an early diagnosis of PLL is necessary to establish its true course and that the prognosis may be better than originally thought.