This issue of Mathematische Nachrichten is dedicated to Leonid Romanovich Volevich who passed away on 16 April 2007 after severe illness. The research of L. R. Volevich had, and still has, great influence on the theory of partial differential equations. His contributions opened new branches and directions of this theory and are characterized by the depth and relevance of his research. Leonid Romanovich Volevich was born in Moscow on 11 July 1934. Following his passion for Mathematics, he entered the Mechanics and Mathematics Department of the Moscow State University in 1952. He finished his diploma as a participant of O. Oleinik's seminar in 1957 and became a Ph.D. student of K. I. Babenko. His Ph.D. thesis entitled "Local properties of solutions of systems of partial differential equations" was defended in 1960 at the applied mathematics division of the Steklov Institute of Mathematics of the Russian Academy of Science. In his mathematical career, L. R. Volevich always worked within this institute which later became the Keldysh Institute of Applied Mathematics of the Russian Academy of Science. In 1971, Volevich defended his D.Sc. thesis entitled "Investigations of nonhomogeneous pseudo-differential operators (questions on the regularity of solutions, the Cauchy problem)".