Acceleration of neutrons by isomeric nuclei.The inelastic neutron acceleration (INNA) by long living isomeric nuclei is studied. The theoretical estimates of the INNA cross‐sections for thermal neutrons for a number of isomers give the values in the range 0.1 ‐ 102b. Inelastic acceleration of thermal neutrons was observed by152mEu and180mHf, and confirmed the high value of the INNA cross‐sections. As a result of the high probability of acceleration some isomeric nuclei113mIn,115mIn, are not usual moderators but accelerators of neutrons. The use of the INNA reaction for the study of high excited levels and the nature of various nuclear hindrances are disc