The present invention relates to compounds of formula (I), and pharmaceutically acceptable salts and tautomers thereof. Compounds of the present invention are inhibitors of histone deacetylase (HDAC) and are useful for treating cellular proliferative diseases, including cancer. They are also useful for treating neurodegenerative diseases, mental retardation, 10 schizophrenia, inflammatory diseases, restenosis, immune disorders, diabetes, cardiovascular disorders and asthma. ##STR00001##