In blood plasma of 8 healthy volunteers with resuspended lymphocytes incubated with 5-fluorouracil (5-FU) the drug distribution between cells and liquid was assessed by means of HPLC. Rapid accumulation of 5-FU in lymphocytes was proved (the drug concentration on the 3-rd minute is 2.5-fold higher than in plasma) as well as the absence of temporal changes of 5-FU content both in lymphocytes and blood plasma during 30 minutes of experiment.