We have previously demonstrated a dose response relationship in Hodgkin's disease for the combination of BCNU, VP16, Ara C and Melphalan, with the superior efficacy of the BEAM regimen requiring haemopoietic support, compared with miniBEAM. To further exploit this, we have attempted to escalate the VP16 dose in BEAM. The standard etoposide dose is 200 mg/m2 IV for four days. Thirty seven patients with refractory lymphoma received 400 mg/m2/day of etoposide, and 13 patients 600 mg/m2/day, in addition to BCNU, cytarabine, and melphalan. Toxicity and outcome parameters were compared in the preceding 40 patients, who received 200 mg/m2/day etoposide. The toxic mortality with 400 mg/m2/day of etoposide (3%) was identical to that for the standard BEAM regimen (5%). Two procedure related deaths occurred in the highest VP16 dose group (15%). The morbidity of the lower etoposide dose regimens was comparable, but 600 mg/m2/day induced significantly greater gastrointestinal toxicity. Twelve of the 13 patients receiving this dose suffered grade II-IV mucositis, with stomatitis, dysphagia and prolonged diarrhoea; 5 haemodynamically significant gastrointestinal haemorrhage, and 1 fatal toxic colitis. Granulocyte colony stimulating factor did not influence the nonhaematological toxicity. The three month response rates were similar (91%) in all dose cohorts. The maximum tolerable etoposide dose within the BEAM regimen is thus 400 mg/m2 for four days.