The invention relates to novel N-hydroxy-substituted 1,2,3,6-tetrahydropyridine and piperidine derivatives of the formula ##STR1## wherein A, B, D, E, G, I and R are as defined in the specification, m is 0, 1 or 2, with the proviso that:m is 0 or 2, or both G and I are hydrogen, when A is benzyl or halogen-monosubstituted benzyl group; andm is 1, when A is 2-picolyl, as well as their pharmaceutically acceptable acid addition salts. The compounds of formula (I) are useful for enhancing the tolerance of mammals (including man) against hypoxic and/or ischaemic states as well as for treating the degenerative and functional disturbances arising from hypoxic and/or ischaemic results.