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 /= 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.