The goal of work was to evaluate epidemiological features and prognostic factors of infections in elderly patients affected by haematological neoplasms. From 1 May 1989 to 30 April 1994 we observed 765 infectious episodes in 416 patients: 554 in patients younger than 65, 211 in patients aged over 65. No difference in rate of combined- or single-agent antibiotic therapy was present, nor in the rate of patients receiving growth factors. The outcome has been classified as positive, death from infections or death from causes other than infection (NID). When all deaths are considered, younger patients had a lower rate of death (120/554, 22%) than the elderly (59/211, 28%) P = 0.069 (Fisher's exact test). When NID are excluded 77/511 (15%) younger patients and 34/186 (18%) elderly patients died P = 0.34. A significantly higher rate of younger patients had an absolute neutrophil count (ANC) lower than 500/mm3 at the onset: younger patients 322/554 (58%), the elderly 79/211 (38%) P < 0.00001. When only neutropenic (ANC < 500/mm3) patients are considered, the difference in outcome between the two groups is more evident: positive outcome was achieved by 251/322 younger (78%) and by 49/79 elderly patients (62%) P = 0.004; when NID were excluded, positive outcome was achieved by 251/306 younger (82%) and by 49/68 elderly patients (72%) P = 0.066. Taking into account a higher rate of NID, it is possible to achieve an outcome for infection in the elderly that is not significantly different from that in younger patients, when less severe neutropenia is induced. However, among neutropenic patients, the prognosis for infections become poorer in elderly patients. This must be evaluated when aggressive chemotherapy for these patients is being designed.