The Mathematical Essays in this volume pay tribute to Gian-Carlo Rota in honor of his 64th birthday. The breadth and depth of Rota's interests, research, and influence are reflected in such areas as combinatorics, invariant theory, geometry, algebraic topology, representation theory, and umbral calculus, one paper coauthored by Rota himself on the umbral calculus. Other important areas of research that are touched on in this collection include special functions, commutative algebra, and statistics.