Dictyosomelike structures (DLS) are organelles unique to male mammalian germ cells and occur in large numbers in spermatocytes of the guinea pig. Selective staining of DLS with phosphotungstic acid at low pH was used to identify DLS in cell fractions prepared by combined sucrose gradient and differential centrifugation procedures. This staining property was retained in homogenates and permitted DLS to be distinguished from cisternae of Golgi apparatus and most other spermatocyte membranes. DLS were resistant to the homogenization and isolation stresses, at least in regard to their structural integrity. The purity of the DLS fractions was proportional to the purity of spermatocytes derived in the initial cell separation steps. Cell separation and the attainment of good spermatocyte fractions appear critical to the isolation of DLS by these procedures.