A new real-time, scanning slit, confocal microscope designed for the clinical in-vivo examination of the human cornea and anterior segment is demonstrated. The key feature of the in-vivo confocal microscope is the use of two conjugate adjustable slits, and a two-sided oscillating mirror which is used both for scanning and for descanning. The light detection efficiency of this microscope is such that is possible to image both the wing cells, and the basal epithelial cells in the normal, living human eye. This paper also demonstrates the advantage of the slit-scanning confocal microscope over alternative designs based on Nipkow disk pinhole systems. The confocal microscopes based on the Nipkow disk with the pinholes are not capable of imaging either wing cells or basal epithelial cells in the normal in vivo human eye. The images shown in this paper are all from single video frames. No analog or digital image processing was used. The high resolution and high contrast shown in the images that are photographs of single video frames are due to the microscope design.