A sample of white dwarfs is selected from the Sloan Digital Sky Survey(SDSS) Data Release 3 using their reduced proper motions, based onimproved proper motions from combined SDSS and USNO-B data. NumerousSDSS and follow-up spectra (Kilic and coworkers) are used to quantifycompleteness and contamination of the sample; kinematics models are usedto understand and correct for velocity-dependent selection biases. Aluminosity function is constructed covering the range7bol<16, and its sensitivity to various assumptionsand selection limits is discussed. The white dwarf luminosity functionbased on 6000 stars is remarkably smooth and rises nearly monotonicallyto Mbol=15.3. It then drops abruptly, although the smallnumber of low-luminosity stars in the sample and their unknownatmospheric composition prevent quantitative conclusions about thisdecline. Stars are identified that may have high tangential velocities,and a preliminary luminosity function is constructed for them.