A single centre randomized placebo-controlled phase II-study with a random assignment to experimental (EXP) or control (CTR) group. All patients with lymphoproliferative diseases ≥18 years of age, scheduled for myeloablative therapy before autologous stem cell transplantation at the Akademiska University Hospital in Uppsala, Sweden, will be included consecutively during one and a half year. A total of 90 patients (45 per treatment arm) will be accrued for this study. They will be invited by mail to participate in the study a couple of weeks before hospital entry. A random assignment to EXP or CTR will be performed by research nurses not participating in any other way in the study. Patients will be stratified for diagnosis which also means myeloablative therapy (lymphoma (BEAC) or myeloma (high-dose melphalan)), and the groups are expected to be similar in size. One box for each diagnosis (lymphoma and myeloma) will contain equal numbers of randomisation cards for the experimental and control groups, randomly mixed within each box. Cards will be picked consecutively by a research nurse not otherwise involved in the study. The EXP group will receive aprepitant (EMEND®) in combination with standard anti-emetic treatment and the CTR group will receive standard anti-emetic treatment. All treatment will be given in the hospital.