Sonya Kovalevskaya was a distinguished mathematician and considered by her contemporaries to be among the best of her generation. Her work, ideas, and approach to mathematics are still relevant today, while her accomplishments continue to inspire women mathematicians. The academic year 1985-86 marked the 15th anniversary of the Association for Women in Mathematics and the 25th anniversary of the Mary Ingraham Bunting Institute of Radcliffe College, Harvard University - both organizations that have enhanced women's role in mathematics. These two occasions provided a framework for a Kovalevskaya celebration, which included a symposium at Radcliffe College, and special sessions at the AMS meeting in Amherst, Massachusetts, both in October 1985.The papers in this collection were drawn from those two events. The first group of papers contains background material about Kovalevskaya's life and work, including a discussion of how she has been perceived by the mathematical community over the last century. The rest of the papers contain new mathematics and cover a wide variety of subjects in geometry, analysis, dynamical systems, and applied mathematics. They all involve, in one form or another, Kovalevskaya's main areas of interest - differential equations and mathematical questions arising from physical phenomena.