This text is based on a conference held in Switzerland in 1994 that promoted the theoretical and methodological development of crystallographic investigations of aperiodic crystals, including modulated structures, polytypes, incommensurate misfit or composite crystals and quasi crystals.

Fibers of polygonal serpentine - topology, polytypism, twinning and five-fold symmetry, A. Baronnet; new directions in aperiodic tilings, L. Danzer; potential applications of aperiodic (quasi)-crystals, J.-M. Dubois; the structures of decagonal quasicrystals and crystalline phases with periods of 1.2 and 1.6 mm studied by high-resolution electron microscopy, K. Hiraga; titanium-based quasicrystals and related crystalline phases, K. Kelton; non-commutative crystallography, P. Kramer; phonons and electrons in quasiperiodic crystals, T. Janssen; non-conformist crystallography, A.L. Mackay; computer simulation of phase transition mechanisms between incommensurate phases, K. Parlinski; the structure of decagonal phases and their approximants, W. Steurer; crystallography of incommensurate intergrowth compounds, S. Van Smaalen; composite crystal structures and superspace groups, A. Yamamoto. (Part contents).