A polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) system is used to measure phase retardation and birefringence of the human retinal nerve fiber layer (RNFL) in vivo. The instrument records three parameters simultaneously: intensity, phase retardation and optic-axis orientation. 3D data sets are recorded in the optic nerve-head area of a healthy and a glaucomatous eye, and the results are presented in various ways: En-face phase-retardation maps of the RNFL are generated from the recorded 3D data and results are compared with scanning laser polarimetry (SLP). The depth information provided by OCT is used to segment the RNFL in the intensity image and measure the RNFL thickness. From the retardation and thickness data, 2D birefringence maps of the RNFL are derived. Circumpapillary plots of RNFL retardation and thickness obtained by PS-SD-OCT are quantitatively compared with those obtained by SLP.