A review is given of the phenomenon of backbending which is observed in the rotational spectra of deformed nuclei. The phenomenon is interpreted in terms of superconducting-type pairing correlations. This model was previously successful in the description of the low-lying rotational states. Analysis of high-spin rotational states in the backbending region has established a similarity between pairing correlations in nuclei and in superconductors of small linear dimensions. In view of this, low-lying quasiparticle terms of the subshell with high angular momentum j on the Fermi surface assume particular importance (through the dependence of quasiparticle energy on the nuclear rotational frequency). The importance of quasiparticle terms in the analysis of the structure of deformed nuclei is noted. The review covers the period up to the beginning of 1980.