This report describes a simple filtration technique to isolate the parasite Mikrocytos mackini from oyster tissue. The technique is based on successive filtration through filter papers and polycarbonate membrane filters of decreasing mesh using a low vacuum (<8 cm Hg). This technique allows for the recovery of about 1 × 10⁸ parasites (microcells) from about 2 g of heavily infected oyster tissue. About 99% of the particulate material in the final preparation consisted of intact M. mackini.