The authors studied the effect of some antiasthmatic drugs (theophylline, budesonide, sodium cromalyne) and beta-carotene in vitro on spontaneous and PHA-induced proliferation of human peripheral blood mononuclears (PBMN). It was found that the drugs had no effect on spontaneous cell proliferation. But budesonide caused a 4-fold and beta-carotene a 6-fold decrease of the index of PHA-stimulated PBMN proliferation. It is concluded that beta-carotene may be used in clinical practice as an anti-inflammatory agent for bronchial asthma treatment.