The effects of etoposide on body weight, organ weights and the concentrations of putrescine, spermidine and spermine in 14 different tissues were examined in rats that had been given the drug for five consecutive days. Etoposide reduces all polyamines, which are associated with tumor cell growth, in the thymus and reduces polyamines of two kinds in the spleen, heart, small intestine, skeletal muscle and lung but it increases putrescine in the prostate and spleen, and spermine in the large intestine.