This invention pertains to certain carbamic acid compounds of the formula (I), which inhibit HDAC (histone deacetylase) activity: wherein: J is a linking functional group and is independently:—O —C(═O)— or —C(═O)—O — or —C(═O)—; Cy is a cyclyl group and is independently: C3-20carbocyclyl, C3-20heterocyclyl, or C5-20aryl; and is optionally substituted; Q1 is a cyclyl leader group, and is independently a divalent bidentate group obtained by removing two hydrogen atoms from a ring carbon atom of a saturated monocyclic hydrocarbon having from 4 to 7 ring atoms, or by removing two hydrogen atoms from a ring carbon atom of saturated monocyclic heterocyclic compound having from 4 to 7 ring atoms including 1 nitrogen ring atom or 1 oxygen ring atom; and is optionally substituted; Q2 is an acid leader group, and is independently: C1-8alkylene; and is optionally substituted; or: Q2 is an acid leader group, and is independently: C5-20arylene; C5-20arylene-C1-7alkylene; C1-7alkylene-C5-20arylene; or C1-7alkylene-C5-20aryleneC1-7alkylene; and is optionally substituted; and pharmaceutically acceptable salts, solvates, amides, esters, ethers, chemically protected forms, and prodrugs thereof. The present invention also pertains to pharmaceutical compositions comprising such compounds, and the use of such compounds and compositions, both in vitro and in vivo, to inhibit HDAC,and in the treatment of conditions mediated by HDAC, cancer, proliferative conditions, psoriasis, etc.