(from preface)The seventh volume of Advances in Heterocyclic Chemistry includes surveys of four groups of heterocyclic compounds; furans (P. Bosshard and 0. H. Eugster), dithiolium salts (H. Prinzbach and E. Futterer), 1,3,4-oxadiazoles (A. Hetzheim and K. Mockel), and diquinolylme-thanes (G. Scheibe and E. Daltrozzo). Further chapters deal with applications of mass spectrometry to heterocycles (G. Spiteller), an area which has expanded very rapidly of late, and the halogenation of heterocycles (J. J. Eisch). Finally, a summary is given of reviews in the heterocyclic field, classified by subject (A. R. Katritzky and S. M. Weeds), which it is hoped may be of assistance in literature surveys.Suggestions are welcomed for contributions to further volumes; they should be in the form of a short synopsis.Thanks are due to the Editorial Board, the publishers, and the authors for their cooperation.