The human Namalva lymphoma cell line being an established producer, predominantly of alpha interferon, has been reported to enhance interferon synthesis after a preincubation in butyrate containing media. We have performed the corresponding experiments with FS-4 fibroblast cells and show that the synthesis of human beta interferon is adversely affected by this treatment. Both cell types are hyperacetylated by the fatty acid to a comparable extent. However, after the withdrawal of butyrate, the persistence of highly acetylated forms of histone H4 is insufficient in the case of FS-4 to endure the interferon induction period. Concerning fibroblasts, deacetylation proceeds to a hypoacetylated state which is reversed only slowly. With lymphoid cells on the other hand, acetylated H4 specimens are much more stable and persist for more than eight hours in the absence of butyrate. Moreover, the acetylation reactions are supported by other Friend cell stimulators which by themselves are no inhibitors of deacetylase activities.