New semicarbazide derivatives of the formula: ##STR1## wherein R.sup.1 is hydrogen,R.sup.2 is hydrogen, lower alkyl, ar(lower)alkyl, lower alkenyl or aryl,R.sup.3 is lower alkyl, ar(lower)alkyl, lower alkenyl or aryl, orR.sup.2 and R.sup.3 are taken together to form (C.sub.2 -C.sub.6)alkylidene group optionally substituted with aryl or taken together with the adjacent nitrogen atom to form a saturated or unsaturated, 5- or 6-membered heterocyclic group optionally substituted with aryl; orR.sup.1 and R.sup.2 are taken together with the adjacent nitrogen atoms to form a saturated or unsaturated, 5- or 6-membered heterocyclic group or 1,2-diazaspiroalkane-1,2-diyl group,R.sup.3 is hydrogen, lower alkyl, ar(lower)alkyl, lower alkenyl or aryl;R.sup.4 is aryl which may have substituent(s) selected from lower alkyl, halogen, lower alkoxy, lower alkylamino, halo(lower)alkyl, hydroxy, lower alkanoyl, esterified carboxy and carboxy,R.sup.5 is hydrogen or lower alkyl, andX is O or S, provided that the lower alkyl group for R.sup.3 is (C.sub.3 -C.sub.6)alkyl, when R.sup.2 is hydrogen or (C.sub.1 -C.sub.2) alkyl and R.sup.4 is aryl optionally having substituent(s) selected from groups consisting of halogen, lower alkyl, lower alkoxy and halo(lower)alkyl, and pharmaceutically acceptable salts thereof, and processes for preparation thereof and pharmaceutical composition comprising the same.These derivatives and salts thereof are useful as antiinflammatory and analgesic agents.