L. BIELEC, T.C. BOISVERT AND S.G. JACKSON. 1996. A compact battery‐operated, portable field filtration apparatus was developed for efficient recovery of parasites, includingGiardia lambliacysts, from large volumes of water. In conjunction with modified filter elution and processing procedures, the filtration device was evaluated in field trials. To monitor performance of the procedure, a known number ofGiardia lambliacysts were added during filtrations through a control injection assembly. This allowed calculation of cyst recovery at each test site, thereby allowing comparison of percentage recoveries from many diverse water sources. This apparatus and modified method now provide the tools to investigate further extraction and purification techniques to improve overall yield ofGiardia lamblia, other parasites and potentially other organisms such as bacteria and viruse