Butyric acid has many strong effects on gene expression in mammalian and viral systems, as well as in increasing the expression of recombinant DNAs artificially introduced into cultured cells. We screened 14 analogues of butyric acid for their ability to upregulate expression from 3 different recombinant chloramphenicol acetyltransferase expression vectors stably integrated into NIH 3T3 cells that had been transformed by calcium phosphate transfection or electroporation. Butyric acid, 2-bromobutyric acid, 3- bromopropionic acid, 3-mercaptopropionic acid, vinylacetic acid, and butyraldehyde were found to upregulate human immunodeficiency viral long terminal repeat-, SV40 early gene promoter-, and glucocerebrosidase promoter- directed expression of heterologous genes in cultured cells. Three other analogues had lesser effects; and 6 additional analogues had very little, if any, effect. © 1993 Academic Press, Inc.