The growth factors basic fibroblast growth factor (bFGF) and insulin-like growth factor 1 (IGF-I) have been implicated in the pathophysiology of atherosclerosis and restenosis. The Tibetan herbal preparation PADMA-28 (a mixture of 22 plants which is used as an anti-atherosclerosis agent) was tested for its ability to inhibit the mitogenic activity of bFGF and IGF-I, growth factors involved in restenosis, atherosclerosis and tumour progression. DNA synthesis and proliferation of vascular smooth muscle cells, in response to serum bFGF, thrombin, or combinations thereof, were abrogated in the presence of microgram amounts of both the aqueous and organic, partially purified, extracts of PADMA-28. These fractions also inhibited IGF-I-mediated proliferation, migration and invasion of tumour cells responsive to IGF-I. The inhibition by PADMA 28 was reversible upon removal of the PADMA extracts, indicating that the effects were not related to cell toxicity. These and other properties (i.e., anti-oxidant activity) of PADMA-28 may be responsible for its beneficial effect as an anti-atherosclerotic agent, suggesting that this herbal preparation may have potential applications in the prevention of intimal hyperplasia and arterial stenosis secondary to coronary angioplasty and bypass surgery, as well as in the prevention and treatment of other vascular diseases and tumour growth and metastasis.