This volume of the EMS is devoted to applications ofsingularity theory in mathematics and physics. The authorsArnol'd, Vasil'ev, Goryunov and Lyashkostudy bifurcationsets arising in various contexts such as the stability ofsingular points of dynamical systems, boundaries of thedomains of ellipticity and hyperbolicity of partialdifferentail equations, boundaries of spaces of oscillatinglinear equations with variable coefficients and boundariesof fundamental systems of solutions.The book also treats applications of the following topics:functions on manifolds with boundary, projections ofcomplete intersections, caustics, wave fronts, evolvents,maximum functions, shock waves, Petrovskij lacunas andgeneralizations of Newton's topological proof that Abelianintegralsare transcendental.The book contains descriptions of numberous very recentresearch results that have not yet appeared in monographform. There are also sections listing open problems,conjectures and directions offuture research. It will be ofgreat interest for mathematicians and physicists, who usesingularity theory as a reference and research aid.