Abstract: Benzoic acid derivatives represented by the formula (I): ##STR1## wherein R.sub.1 represents hydrogen or lower-alkyl, R.sub.2 and R.sub.4 represent hydrogen, trimethylsilyl, or trimethylgermyl, R.sub.3 represents hydrogen, lower-alkyl, trimethylsilyl, or trimethylgermyl, R.sub.5 represents hydrogen, lower-alkyl, acetyl, or hydroxy, at least one of R.sub.2 and R.sub.3 being trimethylsilyl or trimethylgermyl, and R.sub.6 means hydroxy, lower-alkoxy, or a group of the formula --NR.sub.7 R.sub.8, wherein R.sub.7 and R.sub.8 mean hydrogen or lower-alkyl, and X represents a group of the formula --COHN--, --NHCO--, --COO--, --OCO--, --COCH.dbd.CH--, --COCH.dbd.C(OH)--, or --CH.dbd.CH--, which exhibit excellent effect as differentiation-inducing agents for neoplastic cells, especially leukemia cells, or a therapeutic agent for psoriasis or immune and inflammatory diseases, and a process for the preparation thereof, are disclosed.