Sorafenib inhibits multiple kinases involved in angiogenesis and tumour growth. It is used for second-line treatment of advanced kidney cancer and some forms of liver cancer. A placebo-controlled trial in 80 patients with metastatic kidney cancer showed a statistically significant increase in muscle loss during sorafenib therapy. Skeletal muscle mass fell by about 5% after 6 months of treatment and by 8% after one year. In practice, patients treated with sorafenib should be assessed for muscle wasting. The clinical consequences of muscle wasting--loss of autonomy and walking difficulties--should be considered when weighing the benefits and harms of sorafenib therapy.