This volume contains the proceedings of the international conference on " Operator Calculus and Spectral Theory" in Lambrecht, Germany, Decem ber 9. - 14., 1991, sponsored by the Deutsche Forschungsgemeinschaft, and by the Karl-Weierstrass-Institute of Mathematics, Berlin. The idea was to bring together specialists from different areas of modern analysis, geometry and mathematical physics, in a similar spirit as in the earlier series of conferences of the Karl-Weierstrass- Institute (Ludwigsfelde, 1976; Reinhardsbrunn, 1985; Holzhau, 1988; Breitenbrunn,1990). Berlin, Mainz M. Demuth B....