A preliminary study of acidic -glucosidase in a variety of tissues was carried out in an attempt to develop a test which might be used to detect individuals heterozygous for the genetype associated with generalized glycogenosis in beef Shorthorn cattle. Of the tissues readily available peripheral lymphocytes were chosen as being likely to be the most suitable. It was concluded that, when coupled with genealogical information, assays of -glucosidase in extracts of lymphocytes were useful for identifying heterozygous individuals with a reasonably high degree of probability.