The effects of 1-beta-D-arabinosylcytosine (ara-C) and 5-fluorouracil (5-FU) on body weight, and the contents of putrescine, spermidine and spermine in 14 different tissues were examined in rats given these drugs for 5 days. There were statistically significant increases in all three polyamines in the small intestine, in spermidine in the lung, and in spermine in the thymus, spleen and liver of rats treated with ara-C and 5-FU. Putrescine content in the spleen, heart, muscle and liver, and spermidine and spermine contents in the stomach of the 5-FU-treated rats also showed significant increases.