Abstract: The invention relates to an aqueous two phase extraction (ATPE) augmented precipitation process, which may be used to recover and also partially purify therapeutic proteins, including monoclonal antibodies from a crude multi-component mixture. The process involves the formation of a forward extraction PEG-Phosphate ATPE system in which the target product is preferentially partitioned to the polymer rich phase. A second ATPE back extraction system is then formed by introducing the polymer rich phase from the forward extraction to a new phosphate salt rich phase, causing the product to precipitate at the interface between the two phases. This precipitate is then recovered and resolubilised in a suitable buffer and may be passed on for further purification.