Israel Berstein's mathematical work was primarily in the area of homotopy the- ory, a subbranch of algebraic topology that studies theproperties of spaces remaining invariant under continuous deformation. His earliest contributions, which were col- laborative efforts with Ganea, involved the study of so-called Lyusternik-Schnirelman (I-S) category, a numerical measure of the homotopy-theoretic simplicity of a topo- logical space. This notion has applications to many areas of topology, as well as to other subjects, notably to the study of singularities of realvalued functions. In his work on L-S category, first with Ganea, and later on his own and in collaboration with Hilton, Berstein contributed many important insights, extensions, examples and applications, becoming the foremost authority in the world on this subject. With a similar spirit and expertise, Berstein ran the Department's Senior Honors Seminarand atopology literature seminar for graduate students. This last, known informally as "The Berstein Seminar", was of great importance in the education of several generations of topologists, including one (now senior) member of the faculty. The Department has continued this seminar, now formally naming it "The Berstein Seminar" in his honor. Israel Berstein was appointed an Assistant Professor in the Mathematics Department at Cornell, in 1963 Berstein was promoted to an Associate Professorship, and four years later he became a Full Professor.