This volume summarises the lecture and poster sessions of a NATO advanced workshop held in Edinburgh, July 15th-19th, 1985. The workshop was held to bring together plant scientists of many different disciplines but who share a common interest in the regulatory role of calcium in plant development. Although this volume covers the formal proceedings, an equal length of time was devoted to discussion both in large and small groups. A little of the flavour of the directions and character of the discussions will be found in the final article by David Clarkson which was written to cover this other wise uncovered area of the workshop. The volume reflects much of the current excitement in the field of plant calcium research. Many of the participants are pioneers in their res pective areas and the extent to which the last five years has seen a drama tic unfolding, a complete inversion of the role of calcium from simple macro nutrient to major metabolic and developmental controller is recounted here. The material is new and much of it unpublished. In plant physiology, the eighties may yet be designated the decade of calcium.