The high levels of expression produced by molecular cloning techniques make bacteria particularly useful for producing recombinant proteins. However, these proteins often are difficult to purify, owing to their tendency to aggregate and precipitate within the bacteria as insoluble inclusion bodies. Formation of inclusion bodies is especially common for nonbacterial proteins. Although no single method can be applied to every protein, a number of strategies are available to solubilize inclusion body proteins. This protocol describes one such method.