We have developed a pooled ORF (open reading frame) expression technology, POET, that uses recombinational cloning and proteomics methods (two dimensional gel electrophoresis and mass spectrometry) to identify ORFs that when expressed are likely to yield high levels of soluble, purified protein. Because the method works on pools of ORFs, the procedures needed to subclone, express, purify, and assay protein expression for hundreds of clones are greatly simplified. From a pool of 688 C. elegans ORFs expressed in E. coli, small scale expression and purification of 12 positive clones identified by POET yielded on average 6 times as much protein as negative clones. Larger scale expression and purification of 6 of the positive clones yielded 47 to 374 mg of purified protein per liter. POET pools of ORFs can be constructed, and the pools of the resulting proteins can be analyzed and manipulated, to rapidly acquire information about the attributes of hundreds proteins simultaneously.