Recent advances on diversified 3-D printed passive waveguide devices operating from microwave to terahertz frequencies have been reviewed. Developed by the authors' group, several waveguide filters fabricated using a stereolithography (SLA)-based 3-D printing technique have been presented. They are two X-band bandpass filters based on novel high-quality-factor single-mode and dual-mode spherical cavity resonators, and two W-band bandpass filters based on a slotted rectangular waveguide and a compact on-plate structure. The presented filters demonstrate good agreement between the measured and simulated RF performances. Compared with their conventional counterparts made from copper, these SLA-printed devices exhibit a significant weight reduction over 80% due to the use of nonmetallic printing materials, without any penalty of degrading their RF performances.