There is accumulating clinical data supporting the role of probiotics in human health particularly in benefiting the immune system, strengthening the mucosal barrier and suppressing intestinal infection. Fermented and unfermented dairy products enriched with probiotic bacteria have developed into one of the most successful categories of functional foods. From a functional ingredient perspective, the generation of these live cultures in dried formats is particularly attractive, however, it does present challenges in terms of retaining probiotic functionality during powder manufacture and storage. Both freeze-dying and spray-drying can be used for manufacture of probiotic powders on a large-scale, however, both approaches expose the cultures to extreme environmental conditions. Methods of production of dried probiotic powders should be such that viability is maintained in the dried powders following manufacture, and storage to ensure that an adequate number of bacteria can be delivered in the final product. This review will focus on how this can be achieved through approaches such as optimizing drying technology, and the drying matrix, and by manipulating probiotic bacteria by classical (microbiological) or genetic approaches. (c) 2007 Elsevier Ltd. All rights reserved..