Liquid-crystalline phases are now known to be formed by an ever growing
range of quite diverse materials, these include those of low molecular
weight as well as the novel liquid-crystalline polymers, such phases can
also be induced by the addition of a solvent to amphiphilic systems
leading to lyotropic liquid crystals. Irrespective of the structure of
the constituent molecules these numerous liquid-cl)'Stailine phases are
characterised by their long range orientational order. In addition
certain phases exhibit elements of long range positional order. Our
understanding, both experimental and theoretical, at the molecular level
of the static behaviour of these fascinating and important materials is
now well advanced. In contrast the influence of the long range order;
both orientational and positional, on the molecular dynamics in liquid
Cl)'Stais is less well understood. In an attempt to address this
situation a NATO Advanced Study Institute devoted to liquid ctystal
dynamics was held at n Ciocco, Barga, Italy in September 1989. This
brought together experimentalists and theoreticians concerned with the
various dynamical processes occurring in all liquid crystals. The skills
of the participants was impressively wide ranging; they spanned the
experimental techniques used in the study of molecular dynamics, the
nature of the systems investigated and the theoretical models employed
to understand the results. While much was learnt it was also recognised
that much more needed to be done in order to advance our understanding
of molecular dynamics in liquid Cl)'Stais.