These proceedings represent the current state of research on the topics 'boundary theory' and 'spectral and probability theory' of random walks on infinite graphs. They are the result of the two workshops held in Styria (Graz and St. Kathrein am Offenegg, Austria) between June 29th and July 5th, 2009. Many of the participants joined both meetings. Even though the perspectives range from very different fields of mathematics, they all contribute with important results to the same wonderful topic from structure theory, which, by extending a quotation of Laurent Saloff-Coste, could be described by 'exploration of groups by random processes'.

Preface.- Programme of the Workshop on Boundaries.- Programme of the Alp-Workshop 2009.- Publications of D.I. Cartwright.- Publications of M.A. Picardello.- Publications of V.A. Kaimonvich.- M.J. Dunwoody, An Inaccessible Graph.- J. Parkinson and B. Schapira, A Local Limit Theorem for Random Walks on the Chambers of A2 Buildings.- A. Erschler, On Continuity of Range, Entropy and Drift for Random Walks on Groups.- Y. Guivarch and C.R.E. Raja, Polynomial Growth, Recurrence and Ergodicity for Random Walks on Locally Compact Groups and Homogeneous Spaces.- M. Björklund, Ergodic Theorems for Homogeneous Dilations.- A. Gnedin, Boundaries from Inhomogeneous Bernoulli Trials.- P.E.T. Jorgensen and E.P.J. Pearse, Resistance Boundaries of Infinite Networks.- M. Arnaudon and A. Thalmaier, Brownian Motion and Negative Curvature.- R.K. Wojciechowski, Stochastically Incomplete Manifolds and Graphs.- S. Haeseler and M. Keller, Generalized Solutions and Spectrum for Dirichlet Forms on Graphs.- R. Froese, D. Hasler and W. Spitzer, A Geometric Approach to Absolutely Continuous Spectrum for Discrete Schrödinger Operators.- A. Bendikov, B. Bobikau and C. Pittet, Some Spectral and Geometric Aspects of Countable Groups.- P. Müller and P. Stollmann, Percolation Hamiltonians.- T.S. Turova, Survey of Scalings for the Largest Connected Component in Inhomogeneous Random Graphs.- D. DAngeli, A. Donno and T. Nagnibeda, Partition Functions of the Ising Model on Some Self-similar Schreier Graphs.- I. Krasovsky, Aspects of Toeplitz Determinants.