Escherichia coli is the most widely used prokaryotic system for the synthesis of heterologous proteins. Once an optimal expression system has been constructed, protein production can be enhanced by increasing the production of protein per cell per unit time (specific productivity), or by increasing the cell concentration per unit time (cell productivity). Various high cell-density culture (HCDC) techniques have been developed for growing recombinant and non-recombinant E. coli strains in fed-batch cultures at concentrations greater than 100 grams (dry cell weight) per liter. This article reviews the problems encountered in HCDC of E. coli, and discusses various solutions. Feeding strategies for HCDC of E. coli, and the results obtained using them, are also described.