Generalizations about the morphology and genesis of acid sulphate soils at a regional scale are derived from a review of extensive though patchy soil survey data. A general sequence of sedimentation, accumulation of sulphides and burial of sulphitic material by peat or alluvium of low sulphide content, and a parallel sequence of soil profile development are illustrated by examples of unripe sulphitic soils under a natural tidal regime, artificially drained raw acid sulphate soils and ripe acid sulphate soils at various stages of development. The world pattern has been driven mainly by postglacial sea level change but each regional pattern is determined by its unique sedimentary and geomorphological history. Distinctive patterns occur in deltas and estuaries, and in humid and seasonally dry climates. Very extensive areas of ripe acid sulphate soils in areas that are not known to have experienced falls in relative sea level are ascribed to human activity: forest clearance and soil erosion in catchments causing lower dry season river flows, and piecemeal clearance of peat over the floodplains permitting the dry season water table to fall. The implications for further agricultural development in other comparable areas include the absolute necessity to know the extent of potential acid sulphate soils and to maintain their water table above the sulphide datum. Most effective systems of management have been developed by farmers themselves but the sustainability of these systems is often doubtful due to their detrimental effects on the aquatic ecosystem.