Carboxylic acids with known central nervous system and histone deacetylase (HDAC) inhibitory activities were converted to hydroxamic acids and tested using a suite of in vitro biochemical assays with recombinant HDAC isoforms, cell based assays in human cervical carcinoma HeLa cells and primary cultures from mouse forebrain, and a whole animal (Xenopus laevis) developmental assay. Relative to the parent carboxylic acids, two of these analogues exhibited enhanced potency, and one analogue showed altered HDAC isoform selectivity and in vivo activity in the Xenopus assay. We discuss potential uses of these novel hydroxamic acids in studies aimed at determining the utility of HDAC inhibitors as memory enhancers and mood stabilizers.