This study correlated the patterns of ocular B- and A-scans of intraocular retinoblastoma (RB) with corresponding histopathology sections. It aimed to establish a more objective basis for determining intraocular retinoblastoma by ultrasonography (UTZ) and to determine the degree of malignancy and viability of the tumor cells. New cases of retinoblastoma seen at the University of the Philippines– Philippine General Hospital (UP–PGH) from January 1994 to December 2003 were reviewed. Included were patients who underwent enucleation and whose eyeballs were processed at the UP Institute of Ophthalmology. Those with good quality ocular ultrasonographs (UTZ) and clear matching histopathologic sections were finally selected. Findings were correlated and analyzed. Retinoblastoma (RB) showed multiplicity of lesions on UTZ corresponding to multiple lesions on histopathology. The following characteristic patterns were seen: Very malignant RB or pseudorosettes: fine, grainy densities on B-scan with short to medium broad spikes on A-scan (“V-W” pattern). Moderate differentiation with moderate necrosis and early calcific plaques: fine, dense grainy opacities on B-scan with multiple thin, high spikes admixed with tall, broad spikes of calcium deposits on A-scan. Well-differentiated RB with compact viable cells and no necrosis: large, white densities on B-scan with an initial high spike and high internal reflectivity, sometimes “plateauing,” on A-scan with no calcific deposits. Complete tumor necrosis with calcific plaques: echolucent space with dense, white, plaque-like opacities on B-scan; flat or low spikes mixed with tall, broad spikes corresponding to calcium plaques on A-scan. (Authors' abstract)