Attempts were made to stimulate interferon production in human cell cultures by two related acridin drugs, mepacrine and Acranil. Tilorone was included for comparison. In human embryo lung fibroblasts and in normal human leukocytes only tilorone stimulated some inter-feron production. All three drugs stimulated modest interferon production in two lympho- blastoid cell lines. All three drugs enhanced the Sendai virus-induced interferon production in lymphoblastoid cells.