We used a scanning laser ophthalmoscope (SLO) to attempt better visualization of the posterior vitreous than conventional biomicroscopy. We observed the posterior vitreous using the SLO in patients with age- or disease-related vitreous changes. We compared the results using lasers of several wavelengths. The detailed structure of the posterior hyaloid membrane, its collagen mesh structure with premacular defect, and the prepapillary glial ring were clearly visualized by direct laser illumination. Persistent attachment of the vitreous gel to the macula through the oval defect in the posterior hyaloid membrane was seen even with repeated eye rotations. Short wavelength laser was preferable to a long wavelength one for observing the posterior hyaloid membrane. Vitreous opacities were clearly visualized with all lasers as dark spots with fundus monitoring by retro illumination. Thus in vivo visualization of the posterior hyaloid membrane and vitreous gel was achieved using this new technique, which is more advantageous than the conventional biomicroscopy because of its monochromatic laser delivery system with confocal light detection.