Fluorinated diaminobutane compounds in vivo are inhibitors of gamma-aminobutyric acid transaminase and have the following formula: ##STR1## wherein: R.sub.1 represents hydrogen, C.sub.1 -C.sub.6 alkyl, or phenyl-(C.sub.1 -C.sub.4 alkyl); R.sub.2 represents hydrogen, C.sub.1 -C.sub.6 alkyl, phenyl-(C.sub.1 -C.sub.4 alkyl), or R.sub.4, where R.sub.4 is as defined below; R.sub.3 represents hydrogen, or, except when R.sub.2 represents R.sub.4, R.sub.4, where R.sub.4 is as defined below; each R.sub.4, independently, represents C.sub.2 -C.sub.5 alkylcarbonyl, phenylcarbonyl, phenyl-(C.sub.1 -C.sub.4 alkyl) carbonyl, or an aminocarboxylic acid residue derived by removal of an hydroxy group from the carboxy moiety of an L-aminocarboxylic acid; and p represents 1 or 2, and pharmaceutically acceptable acid addition salts thereof.