We examined the survival of 91 young patients (< or = 55 years) with chronic lymphocytic leukemia from the time of failure of fludarabine therapy, in an attempt to identify those with a poor outcome who may benefit from investigative dose-intensive therapies. The median survival of patients unresponsive to fludarabine (n = 42) was 48 weeks, and only 11% responded to subsequent therapies. The median survival of patients relapsing following a fludarabine-induced remission (n = 49) was 87 weeks, and 83% of those who had received fludarabine as their first therapy (n = 14) responded to further fludarabine-containing therapies, with 60% alive at four years. Only 7% of those relapsing patients who had received fludarabine as salvage therapy (n = 35) responded to subsequent therapies (median survival 72 weeks). The poor outlook for these patients justifies the consideration of innovative dose-intensive therapies, such as bone marrow transplantation, with their attendant risk of toxicity.