Lignans are secondary plant metabolites consisting of two phenylpropane units. Their antineoplastic, cardiovascular and antioxidant activities are discussed in the review. The podophyllotoxin derivatives etoposide and teniposide are used in medical practice as cytostatics. Enterolactone and enterodiol were identified in serum and urine of mammalians. They are formed as metabolic products of intestinal microflora from plant precursors, acting in the organism as phytoestrogens and probably preventing some types of cancer.