The BEACOPP chemotherapy regimen for advanced Hodgkin's disease employs a rearranged schedule permitting a shortened three-week cycle. With haematological growth factor support, the dosages of cyclophosphamide, etoposide and adriamycin could be moderately escalated. The 3-armed multicentre HD9 trial (recruitment 1993-1998; 1300 patients randomised) aimed to compare BEACOPP with the standard COPP/ABVD chemotherapy and to detect and measure the gain in efficacy, if any, due to moderate dose escalation of BEACOPP. Eight cycles were given, followed by local irradiation. The most recent interim analysis, with 689 evaluable patients, circa 40% of all expected events and a median observation time of 27 months, showed significant differences in progression rate (P) and in two-year freedom from treatment failure (F) between the treatment arms, with escalated BEACOPP (P = 2%, F = 89%) better than baseline BEACOPP (P = 9%, F = 81%) better than COPP/ABVD (P = 13%, F = 72%). Survival was not significantly different. Acute toxicity was more severe due to dose escalation, but remained manageable. These preliminary results suggest that BEACOPP improves efficacy. Moderate dose escalation is feasible with G-CSF support and appears likely to make a worthwhile improvement in the cure rate. The results must await confirmation (or otherwise) by the final analysis including all randomised patients and sufficiently mature data.