A confocal reflectance theta line-scanning microscope demonstrates imaging of nuclear and cellular morphology in human skin and oral mucosa in vivo. The illumination and detection are through a divided objective lens pupil, resulting in a theta-microscope configuration. A line is directly scanned in the pupil and descanned onto a linear detector array such that the theta line scanner consists of only seven main optical components. The experimentally measured lateral resolution is 1.0 microm and optical section thickness is 1.7 microm under nominal conditions at 830 nm wavelength. Through full-thickness human epidermis (i.e., in the dermis) the measured lateral resolution is 1.7 microm and the optical section thickness is 9.2 microm. The lateral resolution, sectioning, and image quality in epidermal (epithelial) tissue is comparable to that of point scanning confocal microscopy.