This article focuses on the recent world-wide advances of the biotechnology of the increasingly important fed-batch (or semi-batch) cultivation technique used in microbial processes. The history and characteristics of the fed-batch technique in microbial reactions are reviewed and examples of those fed-batch operations are cited which have greatly increased the productivity of microbial conversions in comparison to conventional batch operation; the various fed-batch techniques will be classified according to the mode of nutrient-feeding. Theoretical mathematical models are compared with experimental results. Fed-batch cultures with automatic feedback control are discussed in detail. Cultivation of high microbial cell concentrations, repeated fed-batch operations, and the start-up of microbial processes are described and, finally, some future prospects of fed-batch techniques in microbial processes are discussed.