In this paper is presented a varied description of the fluid bed process for coating or air suspension coating with emphasis on the most efficient batch fluid bed apparatus (the wurster system) and the ideal continuous fluid bed. Phenomena involved in the process of coating fluidised solid particles are studied. The problem of the application of this technology to coat food particles, in terms of feasibility and profitability, is discussed. A comparison between the batch and the continuous systems will bring out the fact that the continuous fluid bed process is the economically suitable solution for coating food powders, but there are a number of problems that must be overcome to get the ideal or efficient continuous system, which does not exist yet. A short review of all these problems is presented. (C) 2002 Elsevier Science Ltd. All rights reserved.