Hepatocyte growth factor (HGF) is a cytokine produced by myeloma cells. We examined serum HGF levels in a population of young myeloma patients (median age 52 years) treated with high-dose chemotherapy. Sera from 128 myeloma patients at diagnosis and serial samples from 16 patients were analysed. Compared with 62 healthy controls, HGF was elevated at diagnosis in 25% of patients (median 0.48 and 1.08 ng/ml respectively; P < 0.0001). The 95 patients who completed therapy were analysed for the impact of HGF on survival. Median survival was not reached after 77 months in the patient group with normal HGF values (< 1.7 ng/ml, n = 69). In the group with elevated HGF (>/= 1.7 ng/ml, n = 26), median survival was 63 months (P = 0.08). In 16 patients, serum was drawn at diagnosis and at the time of expected disease remission (6 weeks to 3 months after chemotherapy). HGF values declined after treatment in 14 of these patients, from a median of 0.9 ng/ml (0.49-1.65) to 0.42 ng/ml (0.32-0.73) (P = 0.005). Our results show that in young myeloma patients HGF is elevated, and that patients with higher levels had a trend towards poorer prognosis. Treatment with high-dose chemotherapy reduced HGF in the serum of the majority of patients.