Marked loss of body weight and profound waste of both skeletal muscle and white adipose tissue occur in rats into which the ascites hepatoma Yoshida AH-130 has been transplanted, associated with marked perturbations in the hormonal homoeostasis and the presence of circulating tumour necrosis factor and high plasma levels of prostaglandin E2 [Tessitore, Costelli and Baccino (1993) Br. J. Cancer 67, 15-23]. On the basis of previous findings, the present study examined whether the development of cachexia in this model system could be significantly affected by adrenalectomy or by pharmacological treatments that may interfere with proximal or distal mediators of tissue hypercatabolism. In no instance was tumour growth modified. Medroxyprogesterone acetate, an anabolic-hormone-like drug, was completely ineffective. In adrenalectomized animals, although changes such as the elevation of plasma triacylglycerols and corticosterone were corrected, the general course of cachexia was not modified. A partial prevention of muscle waste was observed with acetylsalicylic acid, a non-steroidal anti-inflammatory drug, or with leupeptin, a proteinase inhibitor. Insulin afforded the most significant preservation of muscle protein and adipose-tissue mass, which were maintained close to control values even 10 days after transplantation. The effects of insulin on gastrocnemius muscle and liver protein content were exerted by slowing down protein turnover, mainly enhancing synthesis. Consistently, the total free amino acid concentration in the gastrocnemius of insulin-treated rats 10 days after tumour transplantation was close to that of controls. Although treatment with insulin decreased plasma corticosterone to normal values, it did not modify the circulating level of tumour necrosis factor. On the whole these data show that it seems possible to prevent, at least in part, the tissue waste that characterizes cancer cachexia by purely pharmacological means.